--- title: "uni-ball One P: The Short Pocket Gel Pen Explained" canonical: "https://stationerytimes.com/guides/uni-ball-one-p/" description: "uni-ball One P explained: Mitsubishi Pencil's short, round pocket gel pen, 0.38 and 0.5 mm, UMN-SP codes, UMR refills, 29 colors, yen prices and US sources." category: "Pens" type: "Gel pen" published: 2026-10-31 updated: 2026-10-31 author: "Ellis Penhale" publisher: "Stationery Times" sources: 12 products: - name: "uni-ball One P short retractable gel pen (UMN-SP-38 and UMN-SP-05)" brand: "uni-ball" brand_origin: "Japan" made_in: "Not stated" material: "Plastic body with a metal stabilizer tip and wire clip; rose-gold clip and tip on the rose-gold version" released: "2023-03-15" price_band: "$ (under $5 per pen (multi-packs divided by the count), typical US retail, October 2026)" manufacturer: "Mitsubishi Pencil Co., Ltd." model: "UMN-SP-38 / UMN-SP-05" mpn: "UMNSP38.38" gtin: "4902778302903" url: "https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P.html" --- # uni-ball One P: The Short Pocket Gel Pen Explained > The uni-ball One P (UMN-SP) is Mitsubishi Pencil's short, round pocket version of the uni-ball One gel pen, on sale in Japan since March 15, 2023 at ¥550 (about US$3.50). It uses the One's black pigment gel ink in 0.38 or 0.5 mm, a metal stabilizer tip and the same UMR refills, in matte candy colors. - URL: https://stationerytimes.com/guides/uni-ball-one-p/ - Category: Pens - Author: Ellis Penhale - Published: 2026-10-31 - Updated: 2026-10-31 ![uni-ball One P short gel pen in Mandarin Orange drawn to scale, 116.8 mm long and 13.9 mm across the barrel](https://stationerytimes.com/images/raster/uni-ball-one-p-illustration-16x9.png?v=521dff3f) *The uni-ball One P in Mandarin Orange, 116.8 mm long (drawn at 1 mm = 7.69 px; size from a retailer listing).* Original illustration made for this guide. © Stationery Times. 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 One P short retractable gel pen (UMN-SP-38 and UMN-SP-05) | uni-ball (by Mitsubishi Pencil Co., Ltd.) | Japan | Not stated | Plastic body with a metal stabilizer tip and wire clip; rose-gold clip and tip on the rose-gold version | 2023-03-15 | $: under $5 per pen (multi-packs divided by the count) | - Made in (uni-ball One P short retractable gel pen (UMN-SP-38 and UMN-SP-05)): Not stated. Mitsubishi Pencil's Japanese product pages and press releases and the US listings we read on October 31, 2026 don't state a country of manufacture. ### uni-ball One P short retractable gel pen (UMN-SP-38 and UMN-SP-05) colors - Body colors (12 standard, 17 special edition): Mandarin Orange (0.38 mm); Coffee (0.38 mm); Soda (0.38 mm); Peach (0.38 mm); Mint (0.38 mm); Banana (0.5 mm); Yogurt (0.5 mm); Grape (0.5 mm); Papaya (special edition, limited, 0.38 mm); Cherry (special edition, limited, 0.5 mm); La France (rose-gold version) (rose-gold clip and tip, 0.38 mm); Yogurt (rose-gold version) (rose-gold clip and tip, 0.5 mm); Cider (special edition, translucent, limited, 0.38 mm); Raspberry (special edition, translucent, limited, 0.38 mm); White Mint (special edition, limited, 0.38 mm); Cheese (special edition, limited, 0.38 mm); Rose Milk (special edition, limited, 0.5 mm); Black Sesame (special edition, limited, 0.5 mm); Mint (Munyu design) (special edition, limited, printed design, 0.38 mm); Yogurt (Munyu design) (special edition, limited, printed design, 0.38 mm); AC Soda (special edition, limited, printed design, 0.38 mm); AP Cheese (special edition, limited, printed design, 0.38 mm); AK Grape (special edition, limited, printed design, 0.5 mm); AP White Mint (special edition, limited, printed design, 0.5 mm); M Savon (texture color, 0.38 mm); M Peony (texture color, 0.5 mm); D Lavender (special edition, limited, texture color, 0.38 mm); D White Tea (special edition, limited, texture color, 0.5 mm); G Irogami (special edition, limited, texture color, 0.38 mm, sold with a ZENTO refill). - Ink in the box: Black (all One P pens, 0.38 and 0.5 mm). - Per Mitsubishi Pencil Japan (https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P/umnsp.html), checked 2026-10-31. The 29 body colors on Mitsubishi Pencil's three Japanese One P pages (regular, rose-gold version, texture color), with names translated or romanized from the Japanese. Every pen holds black ink. Hakka is mint and Mikan is mandarin orange; a few names use the maker's letter prefixes (AC, AP, AK, M, D, G), whose meaning it doesn't explain. Tints were sampled from the maker's product photos; Cider and Raspberry are translucent barrels, so their tint is the front cone. Shops stock different colors; check the listing. ## Key takeaways - Mitsubishi Pencil announced the One P on February 28, 2023 and put it on sale in Japan on March 15, 2023, at ¥550 (about US$3.50) including tax, in 8 body colors. - The P stands for Pocket: a short, thick, rounded body with a wide, short clip and a metal stabilizer tip. - It takes the same UMR-38S (0.38 mm) and UMR-05S (0.5 mm) refills as the uni-ball One, at ¥110 (about US$0.70) each in Japan. - One Singapore retailer lists it at 11.68 cm long and 13.8 g; Mitsubishi Pencil publishes no dimensions. - uni's US store sells 0.5 mm sets: a 4-pack in Peach, Banana, Coffee and Mint and a limited Yogurt and La France duo, both in our $$ band ($5–20). ## What is the uni-ball One P? **It is a short, round pocket version of the uni-ball One gel pen, sold by Mitsubishi Pencil in Japan since March 15, 2023.** The company announced it on February 28, 2023 at ¥550 (about US$3.50) including tax, in 8 matte "candy" body colors and two ball sizes. It keeps the [uni-ball One](https://stationerytimes.com/guides/uni-ball-one/)'s dark pigment gel ink, which Mitsubishi Pencil says uses large bead-pack pigment particles that stay on the paper's surface, and a movable clip, here in a wider, shorter shape. Mitsubishi Pencil's tagline for it is "round and cute, with a refined feel that fits in your hand." ## uni-ball One P specs | Spec | Value | |---|---| | Maker | Mitsubishi Pencil Co., Ltd., Japan | | Models | UMN-SP-38 (0.38 mm) · UMN-SP-05 (0.5 mm) | | Mechanism | Click (push button) | | Ink | Black pigment gel; every One P pen is black | | Tip | Metal stabilizer mechanism | | Length | 11.68 cm (4.6 in), one retailer listing | | Thickness | 13.9 mm barrel, 19.2 mm with the clip, one retailer listing | | Weight | 13.8 g, one retailer listing | | Refill | UMR-38S · UMR-05S, shared with the uni-ball One | | Japanese list price | ¥550 (about US$3.50) including tax for regular colors | | Made in | Not stated | Mitsubishi Pencil publishes no length or weight for the One P on the pages we read. The size row comes from one Singapore retailer's listing (Stationery World) and could include packaging, so treat it as approximate until we measure one. ## Why is the One P so short and round? **Mitsubishi Pencil designed it to fit in the hand and in a pocket, with a stabilizer tip so the short body still writes steadily.** Its Japanese page says the knock end is a broad, rounded surface, the clip is a wide, short shape that suits the short body, and the metal tip holder (the stabilizer mechanism) keeps the writing feel smooth. ![uni-ball One P and uni-ball One drawn to scale: 116.8 mm and 139 mm long, 13.9 mm and 10.5 mm thick, 13.8 g and 10 g](https://stationerytimes.com/images/uni-ball-one-p-vs-one.svg?v=53cada61) *On listed sizes the One P is about 22 mm shorter and 3.4 mm thicker than the standard One. Original illustration made for this guide. © Stationery Times.* The metal stabilizer tip is shared with the [uni-ball One F](https://stationerytimes.com/guides/uni-ball-one/), which Mitsubishi Pencil describes as lowering the pen's center of gravity. ## What colors and versions does the One P come in? **Eight regular body colors, a rose-gold version, two regular texture colors and a rotating set of limited editions.** The launch colors were Mandarin Orange, Coffee, Soda, Peach and Mint in 0.38 mm, and Banana, Yogurt and Grape in 0.5 mm, in matte finishes. - **Limited editions.** Papaya (0.38 mm) and Cherry (0.5 mm) arrived in October 2023 at the regular ¥550 (about US$3.50). Later limited sets include translucent Cider and Raspberry, White Mint, Cheese, Rose Milk and Black Sesame, at ¥550 (about US$3.50) to ¥660 (about US$4.20) depending on the series. Several printed-design versions at ¥715 (about US$4.50) carry a Sanrio copyright credit in Mitsubishi Pencil's photos. - **Rose-gold version.** The first One P with a rose-gold clip and tip: La France (0.38 mm) and Yogurt (0.5 mm) at ¥880 (about US$5.60). - **Texture colors.** M Savon and M Peony are regular; D Lavender, D White Tea and G Irogami are limited, the last sold with a ZENTO refill, at ¥660 (about US$4.20) to ¥880 (about US$5.60). Mitsubishi Pencil's pages list limited editions as sold in Japan, and a limited color may be gone by the time you look. Our fact card above shows every color on the three Japanese pages on October 31, 2026. ## What refills does the One P take? **The same refills as the uni-ball One: UMR-38S (0.38 mm) and UMR-05S (0.5 mm).** Mitsubishi Pencil's One P page says the refill is shared across the uni-ball One series and lists both at ¥110 (about US$0.70) including tax on its refill page. We didn't find a US-packaged refill item number, so US buyers usually order Japanese refills from importers. Every One P on the pages we read ships with black ink. The maker doesn't say whether the One's colored refills are meant for the P, so we haven't confirmed that; see our [uni-ball One guide](https://stationerytimes.com/guides/uni-ball-one/) for the ink colors it sells. ## How does the One P compare with the One and the One 3? **The One P is the carry-anywhere body, the One is the slim everyday pen and the One 3 is the three-color twist pen.** | Pen | Body | Ink | Notes | |---|---|---|---| | uni-ball One P | Short, round click pen | Black, 0.38 or 0.5 mm | Metal stabilizer tip; body colors, no ink colors | | [uni-ball One](https://stationerytimes.com/guides/uni-ball-one/) | Slim click pen | Many colors, 0.38 to 0.7 mm | 13.9 cm per JetPens; white US barrel | | [uni-ball One 3](https://stationerytimes.com/guides/uni-ball-one-3/) | Short, thick twist body | Black, red and blue | First 3-color One; 129 mm per JetPens | The same maker's [Mitsubishi Pencil history](https://stationerytimes.com/stories/mitsubishi-pencil-history/) explains how the uni-ball line grew, and our [best gel pens](https://stationerytimes.com/guides/best-gel-pens/) roundup picks gel pens for each job. ## Can you buy the uni-ball One P in the US? **Yes, from uni's own US store and from Japan-import sellers.** On October 31, 2026, uni's US store listed a 4-count 0.5 mm set in Peach, Banana, Coffee and Mint and a limited Yogurt and La France duo with a gold clip, each priced in our $$ band ($5–20) per set. Both are 0.5 mm; we didn't see a 0.38 mm One P there. Per pen the One P is in our $ band (under $5), the same as the yen price. Japan-only colors, sizes and limited editions may not reach US stock. Our [Japan-only pens](https://stationerytimes.com/guides/japan-only-pens/) guide tracks which uni pens have US listings. ## Where is the uni-ball One P made? **Mitsubishi Pencil doesn't state it on the pages we read, and neither do the US listings.** We list it as not stated until we can check a package. ## Frequently asked questions ### What does the P in uni-ball One P stand for? Pocket. Mitsubishi Pencil says the name expresses a pen with a refined feel in the hand that you want to take anywhere, and the body is shorter and rounder than the standard One. ### How long is the uni-ball One P? Mitsubishi Pencil publishes no dimensions. One Singapore retailer lists 11.68 cm long, 1.39 cm thick and 1.92 cm with the clip, at 13.8 g, against 13.9 cm for the standard One at JetPens. ### What refills fit the uni-ball One P? The same UMR-38S (0.38 mm) and UMR-05S (0.5 mm) refills as the uni-ball One, which Mitsubishi Pencil lists at ¥110 (about US$0.70) each. A US-packaged refill item number wasn't in the sources we found. ### Does the uni-ball One P come in colored ink? No. Every One P on Mitsubishi Pencil's pages holds black ink; the colors are body colors. ### How many colors does the uni-ball One P come in? Eight regular body colors at launch, and 29 on Mitsubishi Pencil's three Japanese pages today, counting limited editions, the rose-gold version and the texture colors. Limited colors sell out and rotate. ### What is the uni-ball One P rose-gold version? A version with a rose-gold clip and tip, first announced in October 2023 in La France (0.38 mm) and Yogurt (0.5 mm). Mitsubishi Pencil lists it at ¥880 (about US$5.60). ### Is the uni-ball One P sold in the US? Yes. uni's US store lists 0.5 mm sets and a limited Yogurt and La France duo, so the US range is narrower than Japan's 29 colors and offers no 0.38 mm option in the pages we read. ### Is the uni-ball One P refillable? Yes. It is a click pen with a standard One refill, so you can swap in a new UMR refill when the ink runs out. ## Sources - [三菱鉛筆: ユニボール ワン P (Mitsubishi Pencil product page, read in full: concept, stabilizer tip, shared refills, three lineups; October 31, 2026)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P.html) - [三菱鉛筆: ユニボール ワン P ラインナップ (regular colors and limited editions: order codes, JAN, prices; October 31, 2026)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P/umnsp.html) - [三菱鉛筆: ユニボール ワン P ローズゴールドver. (rose-gold version: UMN-SPG, ¥880)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P/umnspg.html) - [三菱鉛筆: ユニボール ワン P テクスチャカラー (texture colors: UMN-SPT)](https://www.mpuni.co.jp/products/ballpoint_pens/gel/uniball_one/one_P/umnspt.html) - [三菱鉛筆 press release: 『uni-ball one P』新発売 (February 28, 2023: on sale March 15, ¥550, 8 colors, name, stabilizer, refills)](https://www.mpuni.co.jp/company/press/20230228-53028.html) - [三菱鉛筆 press release: 『ユニボール ワン P コハクトウカラー』＜一部数量限定＞発売 (October 11, 2023: Papaya, Cherry and the rose-gold version)](https://www.mpuni.co.jp/company/press/20231011-53189.html) - [Impress Watch: 三菱鉛筆、ころんとしたフォルムのボールペン「uni-ball one P」 (March 1, 2023: on-sale date and price confirmed)](https://www.watch.impress.co.jp/docs/news/1481975.html) - [uni US store: uniball One P 4-count set, 0.5 mm, Peach, Banana, Coffee and Mint (read October 31, 2026)](https://www.unibrands.co/products/uniball-one-p-gel-pen-5mm-black-ink-peach-banana-coffee-and-mint-barrel-colors-4-count) - [uni US store: uniball One P limited edition duo, Yogurt and La France, 0.5 mm (read October 31, 2026)](https://www.unibrands.co/products/uniball-one-p-gel-pen-5mm-black-ink-yogurt-and-la-france-2-count) - [Stationery World (Singapore): Uniball One SP UMN-SP.38 (1.39 × 1.92 × 11.68 cm, 13.8 g; read October 31, 2026)](https://stationeryworld.com.sg/uni-mitsubishi-pencil-uniball-ball-one-sp-umn-sp38) - [Yoseka Stationery: Uni-ball One P 0.38 mm (March 2023 release; English color names)](https://yosekastationery.com/products/uni-ball-one-p-0-38mm) - [JetPens: Uni-ball One, a comprehensive guide (standard One length and weight)](https://www.jetpens.com/blog/Uni-ball-One-A-Comprehensive-Guide/pt/1041)