Tombow MONO Zero Eraser: 2.3 mm Round Tip & Refills
The Tombow MONO Zero is a refillable pen-style eraser from Japan's Tombow. The round version (US item 57305) has a 2.3 mm eraser tip that clicks out less than 1 mm at a time, in a pen about 120 mm (4.7 in) long. It refills with ER-KUR sticks and erases single letters without touching nearby lines.
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Product facts
- Product
- Tombow MONO Zero eraser, round 2.3 mm tip (57305 / EH-KUR)
- Brand
- Tombow
- Brand origin
- Japan
- Made in
- Japan*
- Material
- Plastic barrel (at least 40% recycled) with metal guide pipe; synthetic rubber eraser, non-PVC, phthalate-free (Tombow)
- Price range
- $$$5–20 per item
Notes on these facts
- Made by Tombow Pencil Co., Ltd.. Made in Japan: STL Art Supply says the MONO Zero 2.3 mm eraser is made in Japan, and Officeworks in Australia lists Japan as the country of manufacture for its black round MONO Zero. Tombow's Japanese page doesn't state a country, and we found no reliable origin for the ER-KUR refills. Source. Price: example listing.
- 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
- The round tip is 2.3 mm across; the rectangular MONO Zero's tip is 2.5 × 5 mm, per Tombow.
- Tombow says each click advances the eraser by less than 1 mm, using its own indirect-chuck mechanism.
- The Hobonichi store lists the pen at 8.5 × 120 mm (4.7 in), and each refill stick at 2.3 × 50 mm.
- Tombow Japan lists the pen at ¥495 (about US$3.10) and a 2-stick ER-KUR refill at ¥231 (about US$1.50), with tax.
- It won a Good Design Award in 2008, and Red Dot and iF design awards in 2010, per Tombow.
What is the Tombow MONO Zero?
It’s a refillable eraser shaped like a mechanical pencil: a thin eraser stick clicks out of a long metal guide pipe. Tombow, the Tokyo maker of the MONO 100 pencil, sells it with two tip shapes, round and rectangular, and says the round one can correct details as small as a decimal point.
Tombow’s Japanese page lists a Good Design Award in 2008 and Red Dot and iF design awards in 2010. In the US, Tombow USA sells the silver round pen as item 57305.
Tombow MONO Zero round specs
| Spec | Value |
|---|---|
| Maker | Tombow Pencil Co., Ltd. (Japan) |
| Model | EH-KUR (Tombow Japan); 57305 in the US (silver barrel) |
| Tip | Round, 2.3 mm (0.09 in) |
| Advance | Less than 1 mm per click (Tombow) |
| Pen size | 8.5 × 120 mm (4.7 in), per the Hobonichi store |
| Eraser | Light-touch synthetic rubber; non-PVC, phthalate-free |
| Barrel | At least 40% recycled plastic, metal guide pipe |
| Refill | ER-KUR, 2 sticks per pack, each 2.3 × 50 mm |
| Price in Japan | ¥495 (about US$3.10) pen; ¥231 (about US$1.50) refill pack, with tax |
| Price band | $$ ($5–20 per eraser in the US) |
| Made in | Japan (per retailers) |
Tips, the click mechanism, materials and prices come from Tombow’s Japanese page; the pen and refill sizes come from the Hobonichi store. Tombow doesn’t publish a weight in the sources we found.
How small is the 2.3 mm tip?
Small enough to take out one letter, a dot or a stray hatch line while leaving the rest. A block eraser like the Staedtler Mars plastic is 23 mm wide, ten times wider.
Because the stick is thin, it bends if you push hard. Tombow’s short-pitch knock feeds less than 1 mm per click, so two or three clicks are usually enough; retract the eraser into the holder when you’re done.
Round or rectangular: which MONO Zero should you get?
Get the round one for precision; get the rectangular one for straight edges. The rectangular EH-KUS has a 2.5 × 5 mm tip, about twice the area, which clears a whole word or a strip of a drawing faster.
| MONO Zero round | MONO Zero rectangular | |
|---|---|---|
| Tombow code | EH-KUR | EH-KUS |
| Tip | 2.3 mm round | 2.5 × 5 mm |
| Refill | ER-KUR | ER-KUS |
| Best for | Single letters, dots, highlights in drawings | Edges, lines, small areas |
Refills aren’t shared: each shape takes its own stick. If you draw, owning both is common; for note-taking, the round one is enough.
How do you refill it?
Hold down the knock button and push the new ER-KUR stick, still in its plastic rod, into the front of the tip. That is Tombow Japan’s instruction; some retailers, such as STL Art Supply, describe loading from the back instead, so follow the leaflet in your pack.
Each refill pack holds 2 sticks, and the Hobonichi store lists each at 2.3 × 50 mm. We haven’t counted how many letters one stick erases; it depends on the paper and the pencil grade.
What should you pair it with?
Pair it with a fine mechanical pencil or a hard-grade wood pencil. Fine lines from a Pentel Twist-Erase III or a MONO 100 in H are where a pinpoint eraser saves the most work.
If you’d rather carry one tool, the Tombow MONO Graph is a shaker mechanical pencil with a twist-out MONO eraser in its top.
For clearing large areas, keep a block eraser too. The Pentel Hi-Polymer and the Staedtler Mars plastic are the two best-selling block erasers we cover.
Where is the Tombow MONO Zero made?
Retailers list the pen as made in Japan. STL Art Supply says so for the 2.3 mm eraser, and Officeworks in Australia lists Japan as the country of manufacture for its black round MONO Zero.
Tombow’s Japanese page doesn’t name a country, and we didn’t find a reliable origin for the refills.
Frequently asked questions
How big is the Tombow MONO Zero eraser tip?
Tombow lists the round MONO Zero's tip at 2.3 mm (0.09 in) and the rectangular version's at 2.5 × 5 mm, which covers more paper per stroke but is less pinpoint.
Round or rectangular MONO Zero: which should I buy?
Buy the round one for single letters, decimal points and fine detail in drawings. Choose the rectangular one if you want a straight edge for cleaning up lines and slightly larger areas.
What refill does the round MONO Zero take?
It takes Tombow ER-KUR round refills, 2 sticks to a pack; the Hobonichi store lists each stick at 2.3 × 50 mm. The rectangular pen takes ER-KUS instead, and the two aren't interchangeable.
How do you refill a Tombow MONO Zero?
Tombow Japan says to hold down the knock button and push the new stick, still in its plastic rod, into the front of the tip. Some retailers describe loading from the back, but Tombow's own instructions say the tip.
Does the MONO Zero erase ink?
No, it's sold as a pencil eraser. Tombow describes a light-touch synthetic rubber that erases with little pressure, and we haven't tested it on ink or colored pencil yet.
Is the Tombow MONO Zero PVC-free?
Yes. Tombow Japan lists the eraser as non-PVC and free of phthalates, and says the barrel is at least 40% recycled plastic.
Where is the Tombow MONO Zero made?
STL Art Supply and Officeworks list it as made in Japan. Tombow is based in Tokyo, and its own page doesn't state a country, so check the packaging if origin matters.
Sources
- モノゼロ (Tombow Japan product page, "MONO Zero": 2.3 mm round and 2.5 × 5 mm tips, under 1 mm per click, refill from the tip, EH-KUR and ER-KUR codes and prices, 40% recycled plastic, awards)
- Tombow USA: MONO Zero Eraser, Silver, Round (SKU 57305, 2.3 mm)
- Tombow USA: Refill 2-Pack, MONO Zero Eraser, Round Tip (SKU 57316)
- Tombow Europe: MONO zero eraser pen, classic round tip (EH-KUR; 2.3 mm round and 2.5 × 5 mm rectangular tips)
- Hobonichi Techo store: MONO zero (8.5 mm × 120 mm; refill 2.3 × 50 mm)
- Vaessen Creative: Tombow MONO zero precision eraser, square tip 2.5 mm (EH-KUS11)
- STL Art Supply: MONO Zero 2.3 mm eraser (made in Japan)
- Officeworks: Tombow MONO Zero black round eraser (country of manufacture Japan)
- Fred Aldous: MONO Zero eraser, round tip