--- title: "uni-ball Signo DX UM-151: Fine Gel Pen in 31 Colors" canonical: "https://stationerytimes.com/guides/uni-ball-signo-dx-um-151/" description: "uni-ball Signo DX (UM-151) explained: a capped pigment gel pen in 0.28, 0.38 and 0.5 mm, 31 colors in 0.38 mm, 13.8 cm, 11 g, UMR-1 refills, US buying tips." category: "Pens" type: "Gel pen" published: 2026-10-22 updated: 2026-10-24 author: "Ellis Penhale" publisher: "Stationery Times" sources: 6 products: - name: "uni-ball Signo DX (UM-151) gel pen, 0.38 mm, black" brand: "uni-ball" brand_origin: "Japan" made_in: "Not stated" material: "Clear plastic barrel, rubber grip, plastic cap and clip; water-based pigment gel ink" price_band: "$ (under $5 per pen (multi-packs divided by the count), typical US retail, October 2026)" manufacturer: "Mitsubishi Pencil Co., Ltd." model: "UM-151" mpn: "UM151.24" gtin: "4902778556108" url: "https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/signo/um_151.html" --- # uni-ball Signo DX UM-151: Fine Gel Pen in 31 Colors > The uni-ball Signo DX is the capped fine gel pen Mitsubishi Pencil sells in Japan as the uni-ball Signo UM-151. It comes in 0.28, 0.38 and 0.5 mm with pigment ink, including 31 colors in 0.38 mm, at ¥165 (about US$1.00). JetPens lists it at 13.8 cm capped and 11 g; it takes UMR-1 refills. - URL: https://stationerytimes.com/guides/uni-ball-signo-dx-um-151/ - Category: Pens - Author: Ellis Penhale - Published: 2026-10-22 - Updated: 2026-10-24 ![Capped uni-ball Signo DX UM-151 gel pen drawn to scale at 138 mm, clear barrel and black cap, with an inset of the 0.38 mm tip](https://stationerytimes.com/images/raster/uni-ball-signo-dx-um-151-16x9.png) *The Signo DX 0.38 in black, 138 mm capped (drawn at 1 mm = 5 px).* Original drawing (SVG): . 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) | |---|---|---|---|---|---|---| | uni-ball Signo DX (UM-151) gel pen, 0.38 mm, black | uni-ball (by Mitsubishi Pencil Co., Ltd.) | Japan | Not stated | Clear plastic barrel, rubber grip, plastic cap and clip; water-based pigment gel ink | – | $: under $5 per pen (multi-packs divided by the count) | - Made in (uni-ball Signo DX (UM-151) gel pen, 0.38 mm, black): Not stated. Mitsubishi Pencil's Japanese product page doesn't state a country of manufacture, and the JetPens listing as shown in search results doesn't either. Check the pen or package. ### uni-ball Signo DX (UM-151) gel pen, 0.38 mm, black colors - Ink colors (31 standard, 0 special edition): Black (0.28, 0.38, 0.5 mm); Red (0.28, 0.38, 0.5 mm); Blue (0.28, 0.38, 0.5 mm); Baby Pink (0.28, 0.38, 0.5 mm); Pure Pink (0.28, 0.38, 0.5 mm); Pink (0.28, 0.38, 0.5 mm); Mandarin Orange (0.28, 0.38, 0.5 mm); Orange (0.28, 0.38, 0.5 mm); Golden Yellow (0.28, 0.38, 0.5 mm); Lime Green (0.28, 0.38, 0.5 mm); Green (0.28, 0.38, 0.5 mm); Emerald (0.28, 0.38, 0.5 mm); Sky Blue (0.28, 0.38, 0.5 mm); Light Blue (0.28, 0.38, 0.5 mm); Blue Black (0.28, 0.38, 0.5 mm); Violet (0.28, 0.38, 0.5 mm); Brown Black (0.28, 0.38, 0.5 mm); Light Pink (0.38 mm); Bordeaux Black (0.38 mm); Yellow (0.38 mm); Apple Green (0.38 mm); Green Black (0.38 mm); Blue Green (0.38 mm); Prussian Blue (0.38 mm); Purple (0.38 mm); Lilac (0.38 mm); Brown (0.38 mm); Khaki (0.38 mm); Beige (0.38 mm); Dark Gray (0.38 mm); Gray (0.38 mm). - Per Mitsubishi Pencil Japan (https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/signo/um_151.html), checked 2026-10-24. Ink colors and ball sizes as Mitsubishi Pencil's Japanese UM-151 page lists the single pens (names translated from its Japanese; 紫 as Violet and パープル as Purple): 31 in 0.38 mm, 17 of them also in 0.28 and 0.5 mm. The cap and grip show the ink color. Tints were sampled from Mitsubishi Pencil's product photos. Shops stock different colors; check the listing. ## Key takeaways - Mitsubishi Pencil Japan lists the UM-151 in 0.28 mm (17 colors), 0.38 mm (31 colors) and 0.5 mm (17 colors), each at ¥165 (about US$1.00). - JetPens lists the 0.38 mm at 13.8 cm (5.4 in) capped, 15.3 cm (6.0 in) posted and 11 g with ink. - Refills are the UMR-1 family: UMR-1-28, UMR-1 and UMR-1-05, at ¥88 (about US$0.60) in Japan, in black, red, blue and blue-black. - "Signo DX" is the name importers use; uni-ball doesn't sell the UM-151 in its US range, so US buyers get it from importers such as JetPens. - The black 0.38 mm is code UM151.24, JAN 4902778556108. ## What is the uni-ball Signo DX? **It is the capped, fine-point uni-ball Signo that Mitsubishi Pencil sells in Japan as the UM-151, called Signo DX by importers.** It writes with water-based pigment gel ink, which Mitsubishi Pencil says is smooth and resists bleeding, in more colors than almost any fine gel pen. US pen fans have long treated it as a benchmark: The Gentleman Stationer calls it the micro gel pen it compares all others to, and JetPens names the Signo its top fine-tip gel pen. Because uni-ball doesn't sell it in its US range, people often assume it is discontinued; it isn't. ## uni-ball Signo DX specs | Spec | Value | |---|---| | Maker | Mitsubishi Pencil Co., Ltd., Japan | | Type | Capped gel pen, water-based pigment ink | | Sizes | 0.28 mm (UM-151-28), 0.38 mm (UM-151), 0.5 mm (UM-151-05) | | Colors | 31 in 0.38 mm; 17 in 0.28 and 0.5 mm | | Length | 13.8 cm (5.4 in) capped; 15.3 cm (6.0 in) posted | | Weight | 11 g with ink (barrel 9 g, cap 2 g) | | Refill | UMR-1 family | | Black 0.38 mm code / JAN | UM151.24 / 4902778556108 | | Japanese list price | ¥165 (about US$1.00) | Sizes, colors, codes and prices are from Mitsubishi Pencil's Japanese page; length and weight from JetPens. ## Which Signo DX size should you choose? **0.38 mm for most handwriting and the full color range, 0.28 mm for tiny planner writing, and 0.5 mm for a smoother, bolder line.** ![Signo UM-151 ball sizes at 200 times: 0.28, 0.38 and 0.5 mm with refills UMR-1-28, UMR-1 and UMR-1-05](https://stationerytimes.com/images/uni-ball-signo-dx-um-151-ball-sizes.svg) *The 0.5 mm ball is nearly twice as wide as the 0.28 mm.* Very fine balls feel scratchier on rough paper. The 0.28 mm works best on smooth paper such as Tomoe River or Rhodia, while 0.38 mm is the usual all-rounder. ## What colors does the Signo DX come in? **The 0.38 mm has 31 colors; the 0.28 and 0.5 mm have 17 each.** Beyond black, red and blue, the 0.38 mm range includes blue-black, Bordeaux black, green-black and brown-black, pastels such as baby pink, and muted shades such as khaki, beige and grey. Mitsubishi Pencil also sells a 48-color set code (UM-151 48C), and JetPens sells color sets for the US. ## What refills does the Signo DX use? **UMR-1 refills: UMR-1-28 (0.28 mm), UMR-1 (0.38 mm) and UMR-1-05 (0.5 mm), at ¥88 (about US$0.60) each in Japan.** Mitsubishi Pencil's refill table lists the UMR-1 in black, red, blue and blue-black, so most colored pens are replaced rather than refilled. ## Where can you buy the Signo DX in the US? **From importers of Japanese stationery, chiefly JetPens, which lists single pens by color and size and color sets.** The pen you get is the same UM-151 sold in Japan. A single pen stays in our lowest price band, $ (under $5). If you want a Signo you can pick up at an office-supply store instead, the retractable [Signo 207](https://stationerytimes.com/guides/uni-ball-signo-207/) is uni-ball's US model. ## How does the Signo DX compare with other fine gel pens? **It is capped and offers the most colors; the Hi-Tec-C is finer-feeling and the Signo RT1 is the retractable alternative.** | | Signo DX UM-151 | [Signo RT1](https://stationerytimes.com/guides/uni-ball-signo-rt1/) | [Pilot Hi-Tec-C](https://stationerytimes.com/guides/pilot-hi-tec-c/) | [Signo 207](https://stationerytimes.com/guides/uni-ball-signo-207/) | |---|---|---|---|---| | Mechanism | Cap | Retractable | Cap | Retractable | | Finest size | 0.28 mm | 0.28 mm | 0.3 mm (Japan) | 0.38 mm | | US availability | Importers | Importers | Importers | US stores | | Price band | $ | $ | $ | $ | For a bolder white or metallic Signo, see the [Signo Broad UM-153](https://stationerytimes.com/guides/uni-ball-signo-broad-um-153/). ## Where is the uni-ball Signo DX made? **Mitsubishi Pencil doesn't state the country on its Japanese product page.** The company is based in Tokyo; we list the country as not stated until we can check a pen or package. ## Frequently asked questions ### Is the uni-ball Signo DX discontinued? No. Mitsubishi Pencil's Japanese site still lists the UM-151 in 0.28, 0.38 and 0.5 mm in October 2026. It is hard to find in US stores because uni-ball doesn't sell it in its US range. ### What is the difference between the Signo DX and the Signo 207? The Signo DX (UM-151) is a capped Japanese-market pen in 0.28 to 0.5 mm; the Signo 207 is uni-ball's retractable US pen in 0.38 to 1.0 mm. ### What refill fits the Signo DX? The UMR-1 family: UMR-1-28 for 0.28 mm, UMR-1 for 0.38 mm and UMR-1-05 for 0.5 mm, listed at ¥88 (about US$0.60) in Japan. ### What is the finest Signo DX? The 0.28 mm UM-151-28, which Mitsubishi Pencil calls ultra extra fine (超極細). It is one of the finest gel pens still in production. ### How many colors does the Signo DX come in? Mitsubishi Pencil lists 31 colors in 0.38 mm and 17 each in 0.28 and 0.5 mm, from black and blue-black to lilac, khaki and beige. ### Is Signo DX ink waterproof? It is a pigment gel ink, which Mitsubishi Pencil describes as resisting bleeding. It doesn't publish a waterproof standard in the sources we read, and we haven't tested it. ## Sources - [Mitsubishi Pencil Japan: ユニボール シグノ UM-151 (0.28/0.38/0.5 mm, colors, codes, JAN, ¥165; read October 22, 2026)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/signo/um_151.html) - [Mitsubishi Pencil Japan: ゲルインクボールペン替芯 (UMR-1, UMR-1-28, UMR-1-05 refills for the UM-151)](https://www.mpuni.co.jp/products/ballpoint_pens/refill_gel.html) - [JetPens: Uni-ball Signo UM-151 Gel Pen, 0.38 mm, Black (13.8 cm capped, 15.3 cm posted, 11 g; search listing)](https://www.jetpens.com/Uni-ball-Signo-UM-151-Gel-Pen-0.38-mm-Black/pd/306) - [JetPens: Uni-ball Signo: A Comprehensive Guide (UM-151 also known as Signo DX)](https://www.jetpens.com/blog/Uni-ball-Signo-A-Comprehensive-Guide/pt/639) - [JetPens: The Best Fine-Tip Gel Pens (the Signo as top fine-tip pick)](https://www.jetpens.com/blog/The-Best-Fine-Tip-Gel-Pens/pt/876) - [The Gentleman Stationer: Uni Signo DX gel pen review](https://www.gentlemanstationer.com/blog/tag/Signo+DX)