uni-ball ZENTO Signature: Specs, Ink, Refills & Sizes

Side view of the capped uni-ball ZENTO Signature 0.38 mm with its silver metal body, drawn to scale: 123 mm (4.8 in) long capped, 13.0 mm at its widest, with the magnetic cap and pocket clip — The silver 0.38 mm ZENTO Signature, capped and drawn to scale.

Product facts

Product: uni-ball ZENTO Signature (UB-ZH)
Brand: uni-ball
Brand origin: Japan
Made in: Japan^*
Material: Metal body (aluminium and brass, per The Journal Shop)
Released: February 2025^*
Price range: $$$$20–75 per pen (multi-packs divided by the count)

Notes on these facts

Made by Mitsubishi Pencil Co., Ltd.. Made in Japan: per The Journal Shop's spec sheet (country of origin Japan); Mitsubishi Pencil's Japanese product page doesn't state it. Source. Price: example listing. Released: Japanese release date per Mitsubishi Pencil's January 15, 2025 press release, which says ZENTO was already on sale overseas; we found no earlier overseas date.
Price bands are typical US retail, checked October 2026. Conversions to US dollars are approximate, at October 2026 rates (US$1 = ¥158 = ₩1,330 = NT$32.5 = CN¥6.7 = SEK 9.9 = DKK 6.7 = ₺49.6 = C$1.41 = A$1.43; €1 = US$1.12; £1 = US$1.32; CHF 1 = US$1.21).

Key takeaways

Maker: Mitsubishi Pencil (uni), Japan. The Signature (¥3,300 (about US$21)) is the top model of the uniball ZENTO line, above the Flow (¥1,100 (about US$7)), Standard and Basic (¥275 (about US$1.70)) models.
Uni classifies the ZENTO as a water-based rollerball (水性ボールペン), even though many Western retailers sell it as a "gel pen".
Sizes and colors: 0.38 mm (silver body), 0.5 mm (metallic black) and 0.7 mm (champagne gold, added December 23, 2025), all with black ink.
Refillable with UBR-Z refills at ¥132 (about US$0.80) each in Japan; the same refill fits the ZENTO click and capped pens.
JetPens lists it at 12.3 cm (4.8 in) capped, 13.0 mm at its widest and 22 g; The Journal Shop lists Japan as the country of origin.

What is the uni-ball ZENTO Signature?

The uni-ball ZENTO Signature is the flagship of uniball ZENTO, a line of water-based pens that Mitsubishi Pencil (the Japanese maker of uni-ball) began rolling out to Japanese stores in early 2025. Every ZENTO uses the same newly developed ZENTO ink. The Signature model adds a metal body and a magnetic cap that snaps onto the back of the pen when you write.

The three uni-ball ZENTO Signature ball sizes magnified 200 times: 0.38 mm with a silver body, 0.5 mm with a metallic black body and 0.7 mm with a champagne gold body — The three ZENTO Signature ball sizes at 200× and the body color each one comes in. All write in black ink.

It sits above the cheaper Flow (aluminum grip, ¥1,100 (about US$7)), Standard and Basic (¥275 (about US$1.70) each) ZENTO models, which use the same ink in simpler bodies. Mitsubishi Pencil’s launch release says ZENTO went on sale in Japan on February 3, 2025, after it had already been sold overseas.

Is the ZENTO a gel pen or a rollerball?

Mitsubishi Pencil calls the ZENTO a water-based ballpoint, which in English is usually called a rollerball. On the maker’s site it is filed under water-based pens, separate from gel pens like the uni-ball Signo. The ink is a water-based pigment ink.

Many US retailers, including JetPens, list it as a “gel pen”. If you’re comparing it with other pens, it competes most directly with premium rollerballs and fine gel pens. For everyday gel pens, see our Pilot G2, Pentel EnerGel and Sharpie S-Gel guides.

uni-ball ZENTO Signature specs

Spec	Value
Maker	Mitsubishi Pencil Co., Ltd. (uni)
Model numbers	UB-ZH-38 · UB-ZH-05 · UB-ZH-07
Order code / JAN (0.38 silver)	UBZH38.26 · 4902778322291
Ball sizes	0.38 mm · 0.5 mm · 0.7 mm
Body colors	Silver (0.38) · Metallic black (0.5) · Champagne gold (0.7)
Ink	Black, water-based pigment ink (ZENTO ink)
Cap	Magnetic, posts on the back
Body	Metal (aluminium and brass, per The Journal Shop)
Length, capped	123 mm (4.8 in); 132 mm posted
Diameter	13.0 mm max · 10.7 mm at the grip
Weight	22 g with ink (JetPens); 22.25 g measured by a reviewer
Refill	UBR-Z-38 / UBR-Z-05 / UBR-Z-07
Price in Japan	¥3,300 (about US$21) including tax
Made in	Japan (per retailer spec sheets)

Model numbers, sizes, colors and price come from Mitsubishi Pencil’s Japanese lineup page. Dimensions and weight come from JetPens (The Journal Shop lists 13.2 × 123.3 mm), and the country of origin from The Journal Shop. In 2026 Mitsubishi Pencil also listed a limited 0.5 mm Stone Brass version (UB-ZHT-05) at ¥4,400 (about US$28).

To-scale silhouette of the capped uni-ball ZENTO Signature, 123 mm long and 13.0 mm at its widest point, with a 10.7 mm grip under the cap — The capped ZENTO Signature drawn to scale: 123 mm long and 13.0 mm at its widest.

What’s different about ZENTO ink?

ZENTO ink is a newly developed water-based ink that Mitsubishi Pencil says glides with less friction and bleeds less. The maker makes two claims for it:

Lower friction: an additive acts like a cushion between the ball and the paper. The maker says writing friction is about 40% lower than its earlier water-based pens.
Less spreading and bleed: a second additive is meant to keep lines crisp and reduce bleed-through, a common weakness of water-based rollerball ink.

These are the manufacturer’s figures; we haven’t measured them.

Which size should you choose?

0.38 mm: the finest line. It’s good for small handwriting, planners and thin paper.
0.5 mm: the middle option and a safe everyday choice.
0.7 mm: the boldest, smoothest line. It puts down the most ink, so it’s best on thicker paper.

If you write in small notebooks with thin paper, such as a mini composition book, start with 0.38 or 0.5 mm.

Refills

The Signature is refillable: in Japan the refills are sold as UBR-Z-38, UBR-Z-05 and UBR-Z-07, matching the three ball sizes, at ¥132 (about US$0.80) each. Mitsubishi Pencil says the same refill fits both the click and capped ZENTO pens. JetPens sells the 0.38 mm black refill as UBRZ38.24.

ZENTO Signature vs ZENTO Signature 3-color

On June 25, 2026, Mitsubishi Pencil released a ZENTO Signature 3-color pen, listed at ¥5,500 (about US$35). It keeps the magnetic cap that posts on the back, but you twist a knurled section to bring out black, red or blue ink, in 0.38 or 0.5 mm and two body colors. The original Signature remains the single-color capped model.

Frequently asked questions

Is the uni-ball ZENTO a gel pen?

Not by its maker's definition. Mitsubishi Pencil sells the ZENTO as a water-based ballpoint (a rollerball) and files it under its water-based pens, separate from its gel pens. Many Western retailers still list it as a gel pen. The ink is water-based pigment ink.

What sizes does the uni-ball ZENTO Signature come in?

Three ball sizes: 0.38 mm with a silver body, 0.5 mm with a metallic black body, and 0.7 mm with a champagne gold body. The 0.7 mm version was added in December 2025. All write in black ink.

Is the ZENTO Signature refillable?

Yes. It takes the ZENTO water-based refills sold as UBR-Z-38, UBR-Z-05 and UBR-Z-07 in Japan, at ¥132 (about US$0.80) each; Mitsubishi Pencil says the same refill fits both click and capped ZENTO pens. JetPens lists the 0.38 mm black refill under the code UBRZ38.24.

Where is the uni-ball ZENTO Signature made?

The Journal Shop lists the country of origin as Japan; Mitsubishi Pencil's own page doesn't say. Mitsubishi Pencil, the maker, is a Japanese company based in Tokyo.

How much does the ZENTO Signature cost?

In Japan the list price is ¥3,300 (about US$21) including tax (¥3,000 (about US$19) before tax). Outside Japan it is sold by importers, so prices vary by retailer.

How heavy is the ZENTO Signature?

About 22 g. JetPens lists 22 g with ink (16 g barrel, 7 g cap), and one Japanese reviewer measured 22.25 g. Mitsubishi Pencil doesn't publish a weight.

What is the difference between the ZENTO Signature and the ZENTO Signature 3-color pen?

The Signature is a single-color capped pen. The ZENTO Signature 3-color, released on June 25, 2026 at ¥5,500 (about US$35), keeps the magnetic cap but twists out one of three refills (black, red, blue) in 0.38 or 0.5 mm, in a slimmer body than you'd expect for a multi-pen.

Does ZENTO ink bleed through thin paper?

Mitsubishi Pencil says the ZENTO ink includes an additive that limits spreading and bleed-through. On very thin paper, such as composition book paper, a 0.38 or 0.5 mm tip lays down less ink than the 0.7 mm and is the safer choice.

Sources (9)

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