--- title: "uni-ball Signo RT1: Edgeless Tip, 0.28 to 0.5 mm" canonical: "https://stationerytimes.com/guides/uni-ball-signo-rt1/" description: "uni-ball Signo RT1 (UMN-155) explained: a retractable pigment gel pen with an edgeless tip, 0.28, 0.38 and 0.5 mm, 10 colors each, UMR-82/83/85N refills." category: "Pens" type: "Gel pen" published: 2026-10-22 updated: 2026-10-24 author: "Ellis Penhale" publisher: "Stationery Times" sources: 5 products: - name: "uni-ball Signo RT1 retractable gel pen (UMN-155N), 0.38 mm, black" brand: "uni-ball" brand_origin: "Japan" made_in: "Not stated" material: "Plastic body, rubber front grip, stainless steel tip; 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: "UMN-155N" mpn: "UMN155N38.24" gtin: "4902778142653" url: "https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/rt1/umn_155.html" --- # uni-ball Signo RT1: Edgeless Tip, 0.28 to 0.5 mm > The uni-ball Signo RT1 (UMN-155) is Mitsubishi Pencil's retractable fine gel pen with an edgeless tip: the rim around the ball is rounded off to cut friction. It comes in 0.28, 0.38 and 0.5 mm, each in 10 colors of water-based pigment ink, at ¥165 (about US$1.00) in Japan, and takes UMR-82, UMR-83 and UMR-85N refills. - URL: https://stationerytimes.com/guides/uni-ball-signo-rt1/ - Category: Pens - Author: Ellis Penhale - Published: 2026-10-22 - Updated: 2026-10-24 ![Black uni-ball Signo RT1 retractable gel pen drawn in proportion, with an inset of the edgeless tip](https://stationerytimes.com/images/raster/uni-ball-signo-rt1-16x9.png) *The Signo RT1 in black; the grip and body meet without a visible step.* 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 RT1 retractable gel pen (UMN-155N), 0.38 mm, black | uni-ball (by Mitsubishi Pencil Co., Ltd.) | Japan | Not stated | Plastic body, rubber front grip, stainless steel tip; water-based pigment gel ink | – | $: under $5 per pen (multi-packs divided by the count) | - Made in (uni-ball Signo RT1 retractable gel pen (UMN-155N), 0.38 mm, black): Not stated. Mitsubishi Pencil's Japanese product and refill pages don't state a country of manufacture, and we found no retailer page that states it. ### uni-ball Signo RT1 retractable gel pen (UMN-155N), 0.38 mm, black colors - Ink colors (10 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); Orange (0.28, 0.38, 0.5 mm); Lime Green (0.28, 0.38, 0.5 mm); Green (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). - Per Mitsubishi Pencil Japan (https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/rt1/umn_155.html), checked 2026-10-24. The ten ink colors Mitsubishi Pencil's Japanese page lists for the UMN-155N in each of 0.28, 0.38 and 0.5 mm (names translated from its Japanese); the body is tinted to match the ink. The same page also lists a UMN-155C 0.38 mm version with Cherry Red, Light Pink, Aqua and Black Pink bodies and black ink. Tints were sampled from Mitsubishi Pencil's product photos. Shops stock different colors; check the listing. ## Key takeaways - Mitsubishi Pencil Japan lists the Signo RT1 in 0.28, 0.38 and 0.5 mm, 10 colors each, at ¥165 (about US$1.00). - Its edgeless tip removes the corner at the rim of the stainless steel tip, which Mitsubishi Pencil says reduces friction against the paper. - Refills are UMR-82 (0.28 mm), UMR-83 (0.38 mm) and UMR-85N (0.5 mm) at ¥88 (about US$0.60); the UMR-85N also fits the Japanese Signo 207 (UMN-207-05). - The black 0.38 mm is UMN-155N-38, code UMN155N38.24, JAN 4902778142653. - Mitsubishi Pencil doesn't publish a length or weight for the RT1. ## What is the uni-ball Signo RT1? **It is uni-ball's retractable fine Signo, built around an edgeless tip for a smoother line in 0.28 to 0.5 mm.** Mitsubishi Pencil sells it in Japan as the uni-ball Signo RT1 (UMN-155N) with the tagline "極細なのになめらか": extra fine, yet smooth. It is the click-pen counterpart to the capped [Signo DX (UM-151)](https://stationerytimes.com/guides/uni-ball-signo-dx-um-151/), and JetPens features its edgeless tip in its fine-tip gel pen guide. ## What is the edgeless tip? **The tip's rim around the ball is rounded off, so no sharp corner drags on the paper.** Mitsubishi Pencil says this reduces friction between the tip and the paper, which matters most at 0.28 and 0.38 mm, where fine tips tend to feel scratchy. It pairs that with a stainless steel tip for strength and a spring-loaded tip that stops ink flowing out when the pen sits unused. Mitsubishi Pencil also says it reworked the ink for vivid color, low bleeding and smoother writing while keeping the fine line. ## uni-ball Signo RT1 specs | Spec | Value | |---|---| | Maker | Mitsubishi Pencil Co., Ltd., Japan | | Type | Retractable gel pen, water-based pigment ink | | Sizes | 0.28, 0.38, 0.5 mm (UMN-155N-28 / -38 / -05) | | Colors | 10 per size | | Tip | Stainless steel, edgeless, spring-loaded | | Grip | Rubber over the whole front section | | Refills | UMR-82 / UMR-83 / UMR-85N | | Black 0.38 mm code / JAN | UMN155N38.24 / 4902778142653 | | Japanese list price | ¥165 (about US$1.00); refills ¥88 (about US$0.60) | | Length / weight | Not published | All values are from Mitsubishi Pencil's Japanese product and refill pages. ## Which Signo RT1 size should you choose? **0.38 mm for everyday notes, 0.28 mm for planners and small grids, and 0.5 mm for a bolder line that also shares its refill with the Signo 207.** ![Signo RT1 ball sizes at 200 times: 0.28, 0.38 and 0.5 mm with refills UMR-82, UMR-83 and UMR-85N](https://stationerytimes.com/images/uni-ball-signo-rt1-ball-sizes.svg) *Each size has its own refill code.* ## What does the Signo RT1 look like? **A slim, smooth tube: Mitsubishi Pencil calls it a "one-motion" design, with the grip and barrel joined so the seam barely shows.** The whole front section is rubber, and the body has no steps or ridges, which the maker says gives it a flowing, simple shape. Mitsubishi Pencil's photo of the black 0.38 mm shows an all-black pen with a black clip and knock, which is how we drew it. Its understated look suits an office as much as a planner. ## What refills does the Signo RT1 use? **UMR-82 (0.28 mm), UMR-83 (0.38 mm) and UMR-85N (0.5 mm), each ¥88 (about US$0.60) in Japan.** Mitsubishi Pencil lists the UMR-83 for the older Signo RT (UMN-103) too, and the UMR-85N for the Signo RT (UMN-105), Pure Malt (UMN-515) and Japanese Signo 207 (UMN-207-05). That makes the 0.5 mm the most flexible size: one refill fits several uni-ball bodies. ## Signo RT1 vs Signo DX vs Signo 207 **Pick the RT1 for a fine click pen, the DX for the most colors with a cap, and the 207 for easy US availability.** | | Signo RT1 | [Signo DX](https://stationerytimes.com/guides/uni-ball-signo-dx-um-151/) | [Signo 207](https://stationerytimes.com/guides/uni-ball-signo-207/) | |---|---|---|---| | Mechanism | Retractable | Cap | Retractable | | Sizes | 0.28, 0.38, 0.5 mm | 0.28, 0.38, 0.5 mm | 0.38 to 1.0 mm | | Colors | 10 per size | 31 in 0.38 mm | See its guide | | Tip | Edgeless | Standard | Standard | | Price band | $ | $ | $ | For another fine click pen, compare the [Zebra Sarasa Nano](https://stationerytimes.com/guides/zebra-sarasa-nano/), or see our [best gel pens](https://stationerytimes.com/guides/best-gel-pens/). ## Where is the uni-ball Signo RT1 made? **Mitsubishi Pencil doesn't state the country on its Japanese pages.** The company is based in Tokyo; we list it as not stated until we can check a pen or package. ## Frequently asked questions ### What does edgeless tip mean on the Signo RT1? Mitsubishi Pencil rounds off the corner at the end of the metal tip around the ball, so the tip's rim doesn't scrape the paper. It says this lowers friction and makes fine sizes feel smoother. ### Is the Signo RT1 the same as the Signo DX? No. The Signo DX (UM-151) is capped; the RT1 (UMN-155) is retractable with a different tip and refill. Both come in 0.28, 0.38 and 0.5 mm. ### What refill fits the Signo RT1? UMR-82 for 0.28 mm, UMR-83 for 0.38 mm and UMR-85N for 0.5 mm, per Mitsubishi Pencil Japan, at ¥88 (about US$0.60) each. ### Can I put a Signo RT1 refill in a Signo 207? The 0.5 mm UMR-85N is listed for both the RT1 and the Japanese Signo 207 (UMN-207-05). Check the refill code your US 207 takes before buying. ### How many colors does the Signo RT1 come in? Ten in each of the three sizes, 30 pens in all, according to Mitsubishi Pencil Japan. ### How long is the Signo RT1? Mitsubishi Pencil doesn't publish a length or weight. Our cover is drawn in proportion; we'll add a measurement after our own test. ## Sources - [Mitsubishi Pencil Japan: ユニボール シグノ RT1 (edgeless tip, ink, one-motion design; read October 22, 2026)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/rt1.html) - [Mitsubishi Pencil Japan: ユニボール シグノ RT1 UMN-155N (sizes, 10 colors each, codes, JAN, ¥165; read October 22, 2026)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/signo/rt1/umn_155.html) - [Mitsubishi Pencil Japan: ゲルインクボールペン替芯 (UMR-82, UMR-83, UMR-85N refills and compatible pens)](https://www.mpuni.co.jp/products/ballpoint_pens/refill_gel.html) - [JetPens: The Best Fine-Tip Gel Pens (Signo RT1's edgeless tip)](https://www.jetpens.com/blog/The-Best-Fine-Tip-Gel-Pens/pt/876) - [JetPens: Uni-ball Signo: A Comprehensive Guide](https://www.jetpens.com/blog/Uni-ball-Signo-A-Comprehensive-Guide/pt/639)