Pens and Pencils | Reviews and Data

Uni Boxy 100 Ballpoint Pen

The Uni Boxy 100 is a very unique and interesting pen from Mitsubishi Pencil Co, LTD (Uni-Ball). It was first introduced in 1979 and is very popular with Japanese students.

The Boxy 100 — more often referred to as simply the Boxy — is a standard ballpoint that uses traditional oil-based ink. It has a plastic body that is all one piece including the clip. The refill is click actuated with a side return and is replaceable, but we’ll get into that more later.

The most unique aspect of the Boxy is the body design and where it gets its name. It has a box-like shape with two flat sides and two rounded. The flat sides have a ribbed texture towards the tip for addition grip. The pen is also quite short at about five inches. Its similar in length to a Parker Jotter or a Zebra F-301.

It’s popularity in Japan supposedly has to do with a game students would play. They would extend the refill and lay the pen on a desk with a racecar shaped eraser against the top button. Then using the side release, they would propel the eraser across their desk. Whoever got the eraser the farthest won.

This Uni Boxy is also very affordable. In Japan it costs 100 yen. Here in the US it will cost about $1.75 or you can get a 10-pack for just under $12.

The Boxy is the plastic version of the new Mitsubishi Pencil Co. Limex ballpoint.

Uni Boxy 100 Pen Review

The Boxy 100 is a pretty cool pen. The design is fun and different. It isn’t the finest writing instrument but handles the necessities of a standard ballpoint. For the price I can see why it’s so popular in Japan.

The bodies “boxy” shape was a little off-putting at first, but it grew on me the more I used it. The two curved sides, rounded corners, and the textured grip are surprisingly comfortable — even for someone like me who doesn’t use a standard tripod grip.

The clip seems sturdy and effective. You would have to work at breaking it. It did a good job of keeping in my pocket at work where I have to bend, lean, and stoop. Plenty of opportunities for it to fall out but remained steadfast.

The click mechanism and refilling the pen are where things get interesting. The Boxy has a typical top button for extending the refill to write. Yet, it uses an orange side button to retract. The most popular pen I know of that uses the design is the Fisher AG7. In comparison, the Boxy version is much cheaper and all plastic. But still equally effective.

The click is also quite satisfying as a fidgeter. I likely annoyed my office-mate when using the pen for notes at work. It is quite audible.

When I first received the pen, I looked it over and tried to figure out how to take it apart to change the refill. At first glance, I didn’t see any seems or threads. Nothing that stood out like a typical ballpoint and told me how to get inside. I foolishly thought that it might be disposable and set it aside until I was ready for full-on testing.

One I began testing, I became curious and did some research. I came to find out that it is refillable but in a very interesting way. You use a paperclip or other small pointy type instrument to push the orange return button inside the body. Then pull on the top button to remove it. Then the refill will drop out once the pen is inverted.

While I dislike the fact that I need a tool to replace the refill, it’s still a unique design choice. Being a ballpoint, the refill should last for quite a while as well so changing it will not be frequent.

Writing Experience

The Uni Boxy is a very standard ballpoint, yet it’s pretty decent. I actually enjoy writing with it. It’s rather smooth for a typical ballpoint and the ink is a nice color. It’s a little light for my preferences but is as expected. A hybrid ink is about the only way to get darker.

The Boxy writes almost identically to a Zebra F-301 which is a long-time favorite for me. Once I got used to the body shape, I found I enjoyed using this pen almost as much as the Zebra. The 0.7 mm tip is also quite nice and a good general-purpose size. I’ve found I like a 1.0 mm tip for ballpoints a bit more but I won’t complain.


If you’re looking for a typical ballpoint for everyday use, the Boxy 100 is not a bad choice. It affordable, comfortable, and gets the job done. It’s small and fits in a pocket well. Its actually my preferred size for a pen.

Yes, there are much better writing pens out there like gels and rollerballs. Even hybrid ink ballpoints that are silky smooth. But those are unfair comparisons. This pen lives in the realm of Bic Cristals, PaperMate Write Bros, and other cheap everyday pens. To be honest, I’d rather have the Boxy to fall back on for putting lines on paper than any of the others. The only pen I would recommend that is similar would be the Zebra F-301. The only real advantages it has is a metal barrel and an available 1.0mm tip.

The Uni Boxy 100 is a fun pen and a good ballpoint to have on hand. Maybe you can even race some erasers when you’re bored.

Uni Boxy 100 Ballpoint Pen Information

Street Price Check Price
Manufacturer Uni
Pen Type Ballpoint
Barrel Color White, Black
Barrel Material Plastic
Grip Color White, Black
Grip Material Plastic
Country of Origin Japan
MSRP $2.00
Still Sold Yes
Similar To
Capped? Retractable?Retractable - Top Button
Length Capped / Retracted (cm)12.9
Weight (g)7 grams
Ink Color ShippedBlack
Writing Sizes0.7 mm