---
title: "MUJI Smooth Gel Ink Knock Pen 0.3 mm: Colors & Refills"
canonical: "https://stationerytimes.com/guides/muji-smooth-gel-ink-knock-pen/"
description: "MUJI Smooth Gel Ink Ballpoint Knock Pen 0.3 mm explained: 14.5 cm long, five US colors, quick-drying aqueous gel ink, a clip, refills, price band and origin."
category: "Pens"
type: "Gel pen"
published: 2026-11-01
updated: 2026-11-01
author: "Ellis Penhale"
publisher: "Stationery Times"
sources: 3
products:
  - name: "MUJI Smooth Gel Ink Ballpoint Knock Pen 0.3 mm"
    brand: "MUJI"
    brand_origin: "Japan"
    made_in: "Japan"
    material: "Polycarbonate, ABS resin, steel and polypropylene (per MUJI USA)"
    price_band: "$ (under $5 per pen (multi-packs divided by the count), typical US retail, October 2026)"
    manufacturer: "Ryohin Keikaku Co., Ltd."
    model: "Smooth Gel Ink Ballpoint Knock Pen 0.3 mm"
    gtin: "4550344872703"
    url: "https://www.muji.us/products/smooth-gel-ink-knock-type-ballpoint-pen-0-3mm"
---

# MUJI Smooth Gel Ink Knock Pen 0.3 mm: Colors & Refills

> The MUJI Smooth Gel Ink Ballpoint Knock Pen is a retractable 0.3 mm gel pen with a clear frosted body and a clip. MUJI USA sells it in five colors, lists it at 14.5 cm (5.7 in), says its aqueous ink dries quickly, and gives Japan as the country of origin.

- URL: https://stationerytimes.com/guides/muji-smooth-gel-ink-knock-pen/
- Category: Pens
- Author: Ellis Penhale
- Published: 2026-11-01
- Updated: 2026-11-01

![MUJI Smooth Gel Ink Ballpoint Knock Pen drawn to scale at 14.5 cm with a frosted barrel, clip and knock, beside the 0.3 mm ball magnified](https://stationerytimes.com/images/raster/muji-smooth-gel-ink-knock-pen-illustration-16x9.png?v=f8bd2d18)

*The knock pen at MUJI USA's listed 14.5 cm, with the 0.3 mm ball shown 60 times larger.* Original illustration made for this guide. © Stationery Times. Original drawing (SVG): <https://stationerytimes.com/images/muji-smooth-gel-ink-knock-pen-illustration.svg?v=9181bba8>. Drawings © 2026 Stationery Times, reusable with credit under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).

## Product facts

| Product | Brand | Brand origin | Made in | Material | Released | Price range (typical US retail, October 2026) |
|---|---|---|---|---|---|---|
| MUJI Smooth Gel Ink Ballpoint Knock Pen 0.3 mm | MUJI (by Ryohin Keikaku Co., Ltd.) | Japan | Japan | Polycarbonate, ABS resin, steel and polypropylene (per MUJI USA) | – | $: under $5 per pen (multi-packs divided by the count) |

- Made in (MUJI Smooth Gel Ink Ballpoint Knock Pen 0.3 mm): Japan. MUJI USA's product details give "Country/Region of Origin: Japan" for all five colors. Source: https://www.muji.us/products/smooth-gel-ink-knock-type-ballpoint-pen-0-3mm

- Good for: Left-handed writers, Everyday carry.

## Key takeaways

- MUJI USA lists the pen at 5.7 in (14.5 cm) long with a 0.3 mm nib and a clip, in a clear frosted body.
- Five colors in the US: black, blue, red, blue black and orange.
- The body is polycarbonate, ABS resin, steel and polypropylene, and the ink is aqueous (water-based) gel with a 0.3 mm tip.
- MUJI says the ink is quick-drying and suits left- and right-handed writers; those are maker claims, not our tests, and the pen is 5 mm longer than MUJI's 14 cm cap-type pen.
- MUJI USA gives Japan as the country of origin, and each pen is in our $ band (under $5).

## What is the MUJI Smooth Gel Ink Ballpoint Knock Pen?

**It's MUJI's retractable gel pen with a 0.3 mm tip, a clip and a clear frosted body.** MUJI is the brand of Ryohin Keikaku, the Japanese retailer. MUJI USA tags the pen as a best seller in its stationery range.

MUJI USA says the water-based ink dries quickly, resists bleeding through paper, and has a built-in mechanism that stops the ink drying out or flowing the wrong way. Those are the maker's claims. It also says the frosted body shows how much ink is left.

## MUJI smooth gel knock pen specs

| Spec | Value |
|---|---|
| Maker | MUJI (Ryohin Keikaku Co., Ltd.), Japan |
| Type | Retractable gel pen with clip, refillable |
| Length | 5.7 in (14.5 cm), per MUJI USA |
| Nib | 0.3 mm |
| Ink | Aqueous (water-based) gel |
| Materials | Polycarbonate, ABS resin, steel, polypropylene |
| Colors (US) | Black, blue, red, blue black, orange |
| Barcode (black) | 4550344872703 |
| Made in | Japan (MUJI USA) |

MUJI USA gives no weight, barrel width or refill length for this pen, so the barrel in our drawing is drawn by eye.

## Who is the MUJI smooth gel knock pen for?

**It suits anyone who wants a very fine, quick-drying line in a pen that clips to a notebook.**

- **Left-handed writers:** MUJI USA calls the ink quick-drying and suitable for left- and right-handed writers, at a 0.3 mm nib.
- **Everyday carry:** it is 145 mm (5.7 in) long and the clip fits a pocket, lanyard or closed notebook.

Skip it if you want a broad line: 0.3 mm is the finest of MUJI's gel sizes.

![Bars at 20 times scale showing 0.3, 0.38 and 0.5 mm nominal line widths](https://stationerytimes.com/images/muji-smooth-gel-ink-knock-pen-line-widths.svg?v=d329fc65)

*Nominal widths at 20×: the 0.3 mm line is 0.08 mm finer than the 0.38 mm cap-type pen. Original illustration made for this guide. © Stationery Times.*

## Is the 0.3 mm knock pen the same as MUJI's cap-type gel pen?

**No. It's a separate, finer line with a retractable mechanism.** The [MUJI gel ink pen](https://stationerytimes.com/guides/muji-gel-ink-pen/) is the capped pen in 0.38, 0.5 and 0.7 mm; this knock pen is a single 0.3 mm size.

MUJI USA lists the cap-type pen at 14 cm, so the knock pen is 5 mm longer. For a standard 0.5 mm line, see the [MUJI Gel Ink Ballpoint Knock Pen 0.5 mm](https://stationerytimes.com/guides/muji-gel-ink-knock-pen-0-5mm/). MUJI says its cap and knock bodies share refills in Japan; for this specific 0.3 mm pen, MUJI USA doesn't name a refill, so we haven't confirmed one.

## Which MUJI knock pen color should you choose?

**Pick by job: black or blue black for notes, red and orange for marks and corrections.** MUJI USA sells all five colors at the same price. We don't publish swatches because MUJI USA's page gives no ink tints we could state honestly.


## How does it compare with the Pilot G2 and Zebra Sarasa Clip?

**It's the finest and the plainest: the [Pilot G2](https://stationerytimes.com/guides/pilot-g2/) and [Zebra Sarasa Clip](https://stationerytimes.com/guides/zebra-sarasa-clip/) offer more sizes and are sold in more US stores.**

| | MUJI Smooth Gel Knock | Pilot G2 | Zebra Sarasa Clip |
|---|---|---|---|
| Mechanism | Click | Click | Click |
| Sizes | 0.3 mm only | 0.38 / 0.5 / 0.7 / 1.0 mm | 0.3 / 0.4 / 0.5 / 0.7 / 1.0 mm |
| Body | Clear frosted, with clip | Clear plastic, rubber grip | Plastic, movable binder clip |
| Where to buy | MUJI stores and muji.us | Most US stores | Most US stores |
| Price band | $ | $ | $ |

Our [best gel pens](https://stationerytimes.com/guides/best-gel-pens/) roundup picks one gel pen per job, and the [left-handed writers roundup](https://stationerytimes.com/guides/best-pens-for-left-handed-writers/) covers smear-resistant picks.

## How much does it cost?

**Each pen is in our $ band, under $5.** MUJI USA lists every color at the same single-pen price. The product page was read on November 1, 2026, and prices change.

## Where is the MUJI smooth gel ink knock pen made?

**In Japan: MUJI USA's product details give Japan as the country or region of origin.** MUJI doesn't name the factory.

## Frequently asked questions

### Is the MUJI 0.3 mm knock pen good for left-handed writers?

MUJI USA says the quick-drying ink works whether you write left- or right-handed, and tags the pen for left-handers. We haven't smear-tested it ourselves yet, so treat that as the maker's claim.

### Does the MUJI smooth gel pen have a clip?

Yes. MUJI USA says the clip lets you store the pen in a pocket, on a lanyard or in a closed notebook.

### Can you refill the MUJI smooth gel ink pen?

MUJI USA says yes: when the ink runs out the pen can be refilled. It doesn't name the refill on this page, so check that a refill for the 0.3 mm line is in stock before you buy a stack of pens.

### What colors does the MUJI 0.3 mm knock pen come in?

MUJI USA lists black, blue, red, blue black and orange.

### Is the MUJI 0.3 mm pen finer than the MUJI 0.38 mm?

Yes, by 0.08 mm on paper: 0.3 mm against 0.38 mm. The 0.38 mm is MUJI's cap-type gel pen, covered in our MUJI gel ink pen guide.

### Does the MUJI gel pen carry a California warning?

MUJI USA's page carries a California Proposition 65 warning that names cancer. The page doesn't say which part of the pen triggers it.

### Can I return a MUJI pen bought online?

MUJI USA marks this pen Final Sale, with no refunds or exchanges, on its product page as we read it.

## Sources

- [MUJI USA: Smooth Gel Ink Ballpoint Knock Pen 0.3 mm (length 5.7 in / 14.5 cm; nib 0.3 mm; aqueous ink; polycarbonate, ABS resin, steel, polypropylene; Japan; five colors; read in full November 1, 2026)](https://www.muji.us/products/smooth-gel-ink-knock-type-ballpoint-pen-0-3mm)
- [MUJI USA: Gel Ink Ballpoint Cap Type Pen 0.38 mm (for the cap-type comparison)](https://www.muji.us/products/gel-ink-cap-type-pen-0-38mm)
- [MUJI USA stationery collection (product list, read November 1, 2026)](https://www.muji.us/collections/stationery)