Pen Review: Is the Uni Zento Gel Pen Worth the Hype?

One of the most-discussed releases of the past year has been the Uni Zento gel pen, which has captured the attention of the stationery communities in both Japan and the U.S. In particular, the “Zento Signature” - which features a cap as opposed to your typical retractable mechanism - prompted rushes reminiscent of the Uni Kuru Toga Dive mechanical pencil. While I’ve yet to get my hands on one of these “upscale” models for an extended test drive, I’ve had the opportunity to write with both the standard Zento and the slightly upgraded “Zento Flow” (both retractables) for a couple of weeks now. While I’m not sure I would pay more than standard retail for any version of this pen, the Zento is an excellent gel pen and so far I prefer it over the Uni One and any of the basic Uni Signo “office” inks.

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The Uni Zento Flow Gel Pen in the Jade Colorway, in-hand. I also went with a Canary Yellow standard Zento.

So What’s the Story Behind the Zento?

Uni’s gel pen lineup can be confusing - the company has released multiple iterations of your standard black/blue/red gel pen and left them all on the market simultaneously, the only difference supposedly being different inks that to most people will seem quite similar. The Zento is advertised as formulated for “stress free” writing, which apparently refers to a combination of smoothness and cushion. The Zento is indeed quite comfortable to write with - the pen feels very smooth with little to no scratch, and the ink glides on the page and dries instantaneously. The ink is also advertised as formulated to reduce feathering and bleedthrough, and I can confirm there is none. Now was this actually so much of an issue with Uni’s other pens that it warranted an entirely new product line? I’m not sure, but it doesn’t change the fact that the Zento is good.

Ink Comparison: Zento Black Ink (top) has a more matte look, vs. the glossy black Uni One (bottom). To draw a comparison to fountain pen inks, I’d compare the Zento ink to something like Platinum Carbon Black or Sailor Kiwa-Guro, while the Uni One ink is more of a glossy black like Aurora.

How Does the Uni Zento Compare to the Uni One?

As I noted, in addition to the Zento, Uni released the Uni One a few years ago, which was supposed to be another “specialty” ink that’s a step above your standard office gel pen. I’ve found the Uni One and the Zento to offer somewhat different writing experiences, so I can confirm the distinction is real. The One contains an ink formulated to be extremely dark (standard black) and/or vivid (other colors), with a glossier finish. So if you prefer a darker, wet look to your gel ink, you might prefer the Uni One, especially if you’re using the pen for drawing or doing layout work in a bullet journal or planner. The Zento seems better suited to pure writing, as it lays down a remarkably smooth line and, in my opinion, has the more comfortable barrel.

Update: You can now view the Uni Zento companion video review on our YouTube Channel!

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The array of barrel colors available for the Uni Zento standard. There are some great colors available.

Takeaways and Where to Buy

Uni makes a great gel pen, and I surprised myself with how much I enjoyed the Zento as I don’t typically do much writing with gel ink beyond quick notes and annotations. I strongly prefer the barrel on the Zento over the One and pretty much any other standard gel pen - it’s got a nice balance, the perfect diameter for my hand, and on the standard model, a soft texture that’s comfortable over longer sessions. I will also say that the clips on both the Uni Zento and the Uni One are excellent - the wire design is highly functional - with the slight edge to the Zento as it feels a bit tighter on both the standard model and the Flow. That said, if you prefer the barrel on the One but want to try Zento ink, the Zento refills fit the Uni One, and vice-versa.

We currently have a large selection of the standard Uni Zento gel pens available in our shop, as well as a smaller selection of the Zento Flow, with the upgraded barrels. Zentos are priced at $3 and $11, respectively, with extra refills available for $1.75. You can get a nice pen at a reasonable price, or pick up a refill that will fit one of your existing Uni pen bodies.

Come see these pens in person! Visit our shop, currently open Thursday and Friday 1-6pm, and Saturdays 10-6pm. Check this page to keep up to date on our current hours, which may change depending on travel schedules during pen show season.

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You can tell the difference between the clip on a Zento (top and bottom) because it has the round holder, whereas the holder on the One is rectangular.

Uni-Ball One or Zebra Sarasa Grand: A High-End Gel Pen Showdown?

If there's a category of stationery that I've somewhat neglected in my writing over the years, it's the gel pen. Why? Not because I dislike them as a writing instrument; rather, it's because I haven't noticed much innovation from major manufacturers since the late 2010s, with most of the attention in the community paid to third-party machined pen bodies designed to work with the standard refills from the "big pen" companies. Nothing released by Pilot, Uni, Zebra, etc. themselves has caught my eye, until recently.

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The best of both worlds? Gel pens sit somewhere between a ballpoint and rollerball in terms of smoothness, but what sets them apart as a category are the nearly unlimited color possibilities. Shown here are few of Zebra’s “Vintage” ink colors. Three different options for sepia/brown-toned ink?

What Makes a Good Gel Pen?

Gel ink's core selling points are (1) smoothness; (2) paper versatility; and (3) vibrancy. In other words, you get the cleaner lines and feather-resistance of a ballpoint without the messy bleedthrough and smearing common with rollerballs, with the added ability to source refills in pretty much any color you can think of. Personally, I rarely use rollerballs anymore, and while the low-viscosity ballpoint remains my non-fountain pen workhorse of choice, I'll never turn down a good gel pen provided that it flows well and dries quickly.

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The Uni-ball One is a perfect length and diameter. It’s hard to find a gel pen I can comfortably use for longer writing sessions but this one checks most of my boxes.

Uni-ball One "F" Series: My Favorite of Uni's Current Gel Options

Despite the amount of attention Uni receives in the pen and stationery blogosphere, I've mainly used Pilot gel pens over the years, probably more out of habit than anything else because I've never had a Uni pen body that clicked with me. (Pun intended.) That's changed with the Uni-ball One Series F. I actually first tried these pens when my wife and daughter picked up a couple of them at Kinokuniya because they liked the look of the "Earth Texture" series. As it turns out, these are really good pens!

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A close up of the material from the “Earth Texture” pens. I love the mottled look.

The Uni-ball One serves as the vehicle for a "new" gel ink formulation that Uni released a few years ago, which they say contains a proprietary pigmented ink that uses larger particles of pigment to increase the darkness and/or vibrancy of the ink. The initial release had a few hiccups, with reports of skipping and other refill issues. Apparently Uni tweaked the ink formulation and recent manufacturing runs (including all the pens I personally have used) write much better. Personally, I can't tell much of a difference between the Uni-ball One and most other Uni gel ink pens, other than, yes, possibly darker blacks and brighter colors to some degree. What I really like about these pens is the pen body itself.

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A close-up of the clip on the Uni-ball One Series F. I’ve found this clip design to be functional, though I don’t personally use clips all that much anymore.

Uni has foregone a rubberized "cushion" grip in favor of a larger-diameter plastic barrel that I find very comfortable to hold. While there is some texture to the barrel, it's not over-pronounced but enough to keep the pen from slipping in your hand. The "F" series also adds a metal tip which gives the pen better balance than your typical plastic gel pen body, and all versions of the One feature a springy industrial-style clip. Best of all? Because there's no sticky rubber grip, the pen doesn't collect dust and gunk in your desk/bag/pen case like many inexpensive gel pens.

Zebra Sarasa Grand Vintage: A "Professional" Option

Even though the Uni-ball One is a "nice" looking pen, it still has that "inexpensive plastic gel pen look" because, well, it's a relatively inexpensive plastic gel pen and you can't pretend it's something that it's not. As I alluded to above, a source of frustration over the years has been the seeming lack of "professional" first-party gel pen options that feature the same broad range of color options as the less expensive pens. Enter something like the Zebra Sarasa Grand Vintage.

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When you start releasing pens in colors like “Brown-Grey”, you have my attention.

The Zebra Sarasa is a somewhat odd product line, spanning everything from extremely inexpensive office-supply gel pens to the higher-quality "Sarasa Clip" series to even higher-end pens like the Sarasa Grand and Sarasa Grand "Vintage" lines. The Sarasa Grand has a much different feel than something like the Uni-ball One or even the standard Zebra Sarasa - it's a slimmer pen with a metal (aluminum) barrel and a much more substantial feel in the hand. I've seen it described as "sleek," "slender," and "streamlined" - all of these hold true. Zebra recently redesiged this particular model, substituting aluminum for brass and reducing the length of the metal barrel component to make the pen lighter and better balanced. (You can see a comparison photo in yesterday's announcement post.) The barrel has a slightly matte/brushed texture to it, for added grip.

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The full line of colors that we carry. .3mm options in the group on the left, .5mm options on the right. No I can’t name them all.

I've long admired the Sarasa Grand Vintage series from afar, but one thing that I couldn't tell from online advertisements (until I saw them in person and confirmed), was whether the color designation referred to the pen barrel or the ink or both. Turns out it's both! Not only do you have some wild vintage-style barrel colors - mostly muted shades of grey and black-infused tones - but the inks match, and you can purchase all of them in stand-alone refills in either .3mm or .5mm tip sizes. Currently, my favorites have been "Sepia Black," "Red Black" (of course), Blue-Black, and "Camel Yellow." The Sarasa JF refill dries quickly without smearing or smudging and I understand, anecdotally, that it may fit other Japanese gel pen barrels including the Uni-ball One, though I've also heard that they randomly won't fit perfectly from time-to-time and may require modification. YMMV and attempt any mods at your own risk.

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“Camel Yellow”: a gorgeous orange-gold with a matching ink tone.

Takeaways and Where to Buy

So which of these two "high-end" gel pens do I prefer? Honestly, for the complete overall writing experience, probably the Sarasa Grand Vintage. It's a more premium pen, and feels like it. I've been using one of the older models in my personal testing, and while I'm not sure that the redesign would justify replacing a pen you're already happy with, I can absolutely feel a difference with respect to the balance in the 2024 model. Plus, these colors just speak to me. For a lighter weight plastic pen, the Uni-ball One is a solid option that will likely replace the various Signo DX and Signo RT pens that I have in rotation simply because the barrel is that much more comfortable for me to use.

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Both pens have very precise tips, with a .38mm/.3mm size available.

We've carried certain select versions of the Uni-ball One F in our shop for a while, and as I mentioned yesterday, we now stock the Zebra Sarasa Grand Vintage (new 2024 versions). Both of these are relatively inexpensive upgrades for those who want something a bit more “professional” than your standard clear plastic office supply closet gel pen. The Uni-ball One F series pens are priced at just under $5, while the Sarasa Grand Vintage is at $20. Refills for both pens are also available in our shop.

Update: Many of you have asked about our exclusive Sunderland mk1 collaboration, and whether it will be making a return. The answer is yes! I've spoken with Brad at Sunderland and things are underway. Look for an update on a third run later this summer! I'm glad this pen resonated with so many of you and I look forward to its return.

The Gentleman Stationer is supported entirely by purchases from the T.G.S. Curated Shop and pledges via the T.G.S. Patreon Program. We greatly appreciate your support.

New Arrivals: Zebra Sarasa Grand "Vintage" Series Gel Pens (2024 Upgraded Versions)

While the standard Zebra Sarasa gel pen has always seemed a touch too wet for me, I have enjoyed the more specialty Zebra releases, including the Sarasa Clip and other pens that can be imported from Japan. Even then, I was still surprised when I picked up a pen from the Zebra Sarasa Grand “Vintage” series to test early this year and it turned out to be one of the best gel pens that I’ve used in years. I actually enjoyed it so much so that we imported the entire line!

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Zebra’s “Vintage” line contains some insanely good colors, like “Red Black” and “Sepia Black”. Some, but not all, are available in the .3mm tip size as well as your standard (for Japan) .5mm.

We now offer the Sarasa Grand “Vintage” gel pens in both .3mm and .5mm tip sizes, as well as the full range of refills. The Sarasa Grand is Zebra’s “upgraded” Sarasa barrel, similar to Uni’s Jetstream Prime and Pilot’s G2 Limited. Note that the colors refer both to the barrel color and the ink color (i.e., a blue-black pen will have blue-black ink), though you can of course mix and match by purchasing extra refills. Happy Shopping!

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The pens we carry are the new (revised) version of the Sarasa Grand (shown at right). Zebra shortened the metal portion of the barrel slightly to give the pen better balance, and the tip extends further from the opening. I personally think the new barrel is a touch more textured. It can be somewhat hard to find a “professional” looking gel pen, and the brushed aluminum barrels on these pens still look understated even in some of the brighter colors.

New Arrivals: Jetstream 4&1 Multi Pens and Uni-ball One Special Editions!

As a self-proclaimed multi pen connoisseur, it was only a matter of time before I really began building out our own multi pen offerings here in the shop. One of my personal favorites is the Uni Mitsubishi Jetstream “4&1” pen, which features a textured (yet still smooth) bamboo grip section, four different Jetstream .5mm refills, and a .5mm mechanical pencil option. The Uni-ball “One” gel pen showcases Uni’s latest gel pen technology - a new smooth, dark ink formulation in both .38mm and .5mm tip sizes.

Uni-ball One Gel Pens are available in both .38mm and .5mm tip sizes. Refills in the stock pens are black, but extra refills in blue, blue-black, red, and orange are also available for purchase separately.

We currently have interesting versions of both the Jetstream 4&1 multi pen and the Uni-ball One gel pen available in the shop. In addition to the “Bamboo” series of the multi pens, we have Uni-ball One pens in both solid muted colors as well as the “Earth Texture” series. Multi Pens start at $25 and Uni-ball One Pens at $4.50. Refills are also available for both.

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The “Earth Texture” barrels are gorgeous. I’ve not seen anything else quite like this in the gel pen world!

The Gentleman Stationer is supported entirely by purchases from the T.G.S. Curated Shop and pledges via the T.G.S. Patreon Program.

How Fine is "Too Fine"? Comparing Tip Sizes Across Different Pen and Pencil Types

It can be hard to make sense of the different tip sizes in ballpoints, gel pens, and mechanical pencils. Manufacturers tend to denote the tip size in millimeters (or tenths of a millimeter) as opposed to the arguably more descriptive "fine,” "medium,” and “broad” or “bold” typically used in fountain pens and rollerballs. Moreover, the actual corresponding line width isn't always consistent, due to differences between ballpoint and gel ink. For example, a .5mm gel pen might write a wetter line that looks wider than a corresponding .5mm ballpoint.

Since I've spent the past couple of weeks on "day job" projects that have required a lot of travel and non-fountain-pen use, I thought it might be interesting to do a direct comparison of the different widths and test some recent observations.

These days, the only ballpoint pen I use with any regularity is the Uniball Jetstream. And I use ALL the sizes. Even in non-Jetstream pens, I’ve mostly swapped out the original refill for the Parker-style Jetstream SXR-600 (shown at bottom). Shown here are the Jetstream Prime (left) and Jetstream Edge (right).

Ballpoint Example: Uniball Jetstream

It's somewhat difficult to find decent ballpoints that allow you to write a very fine line outside of Uni's Jetstream line. There are exceptions, like the Anterique Mach Ball Pens and the Ohto Refills found in Mark's and Traveler's Company Pens, but these less common Japanese imports are generally limited to the .5mm size, whereas the Jetstream comes in in both .38mm and .28mm line widths.

Since ballpoint refills are typically drier than rollerball or gel pens, you really do get a lot of differentiation between the different line widths. That .28mm can almost be described as a “hairline”, especially with light pressure.

I'm always shocked at how smooth Jetstream refills write, even at the .28mm width. .5mm will always be my personal sweet spot for everyday writing, but it's nice to have the ultra fine options for notetaking and annotation. Currently, I’m only aware of the Jetstream Edge in this ultra-fine .28mm tip, but it’s possible there are others sold in Japan.

The Pilot Hi-Tec-C Coleto has long been my go-to gel multi pen. Check out my original review from 2016!

Gel Pen Example: Pilot Hi-Tec-C Coleto Multi-Pen

The Pilot Hi-Tec-C remains a favorite gel pen, and the Coleto multi-pen version (in all of its various iterations) is probably my all-time favorite option. With gel pens, I tend to prefer the Hi-Tec-C's needle-tip, and I've found the Coleto Multi-Pen refills to resist the flow issues and clogging that can be endemic to the standard Hi-Tec-C.

I don’t have a .7m Hi-Tec-C (or know whether one even exists), so I subbed in a Pilot G2 for the .7mm writing sample.

Personally, the "sweet spot" for me is the .4mm Hi-Tec-C Coleto refill. I find these ever-so-slightly wider and smoother than most ".38mm" refills. This could be an ink issue as opposed to tip size, but I'm speaking from hands-on experience here, not any sort of technical analysis.

Mechanical Pencil Examples: Uni Kuru Toga and Caran d'Ache 888 Infinite

I've only recently begun experimenting with mechanical pencils narrower than .5mm. During my recent trip to NYC, I picked up a .38mm Uni Kuru Toga at Kinokuniya. I'm surprised at how usable this pencil is, even if you do have to be somewhat careful to avoid lead breakage. Generally speaking, a .7mm mechanical pencil will give you a line width closest to a standard woodcase pencil freshly sharpened in a long-point sharpener. The .5mm is my default “I-want-to-write-small-without-worrying-about-lead-breakage” pencil, and the size I use the most frequently. If you use a higher quality pencil lead, a .5mm mechanical pencil can be nearly as break-resistant as a .7mm pencil.

Shown here: the .7mm Caran d’Ache 888 Infinite (sorry, no longer available but the lead is identical to other Caran d’Ache Mechanical Pencils), and two Uni Kuru-Toga pencils in both .5mm and .38mm. I’m aware that .9mm and 1.1mm mechanical pencil sizes exist as well, though they’re less common and at that width, I will probably use a standard woodcase pencil or a 2mm leadholder.

Practical Considerations: Some Parting Thoughts on Choosing a Size

First, the good news: Most ballpoints, gel pens, and mechanical pencils are relatively inexpensive, so the risk of choosing the "wrong line width" is relatively low. You can buy one of each size and write with them for a while before making a larger investment in a broader range of colors or multiple refills.

If you find that you enjoy a certain brand/width combination (for example, a Jetstream in .7mm), you aren’t necessarily limited to buying pens from a single company because you can often find a more universal refill. Shown here is the Jetstream SXR-600, a Parker-style refill that fits ballpoints and rollerballs from many different brands. The Jetstream SXR-200 D1 refill is a great option for most D1 multi pens.

Second, as someone who takes a lot of notes and is a serial annotator - meaning that I obsessively mark up books, articles, and documents as I read them - I tend to find a use case for all of the different sizes. While .5mm is my go-to size for everyday writing, I typically keep a .38mm or .4mm handy, and have been experimenting with the .28mm Jetstream Edge. On the other hand, if you mainly write longhand, such as using your pens and pencils to journal, you may find .7mm the best all around choice. .5mm or wider will give you a smoother writing experience.

Here you can see an overall comparison of the three categories of writing samples above. In general, gel pens write a wider line than their corresponding ballpoint, and mechanical pencils will of course have less “spread” on the page since they don’t use liquid ink. The paper used is the Blackwing “Illegal Pad”, in the ruled format with the classic center dividing line.

Finally, though I'm still working through my thoughts on ultra-fine mechanical pencils, I'm pretty confident that anything finer than .5mm won't make it into my everyday rotation. With a mechanical pencil, you have to worry about lead breakage, and these ultra-fine widths are inescapably more fragile than their .5mm and .7mm counterparts. With a .38mm mechanical pencil, I've found that I have to pay more attention to things like paper texture, which can snag the lead and cause a break.

The Gentleman Stationer is supported entirely by purchases from the T.G.S. Curated Shop and pledges via the T.G.S. Patreon Program. Certain pens and pencils discussed in this post are available for purchase in our shop, so please consider supporting us if you enjoyed this content!