--- title: "TWSBI ECO: Piston Filler, Ink Capacity & Nib Sizes" canonical: "https://stationerytimes.com/guides/twsbi-eco/" description: "TWSBI ECO fountain pen explained: a piston filler holding about 1.76 ml, EF to B and 1.1 mm stub steel nibs, 138.8 mm and 21 g, the ECO-T, and where it's made." category: "Pens" type: "Fountain pen" published: 2026-10-20 updated: 2026-10-20 author: "Ellis Penhale" publisher: "Stationery Times" sources: 12 products: - name: "TWSBI ECO Fountain Pen" brand: "TWSBI" brand_origin: "Taiwan" made_in: "Taiwan" material: "Solid and transparent resin; stainless steel nib" released: "2015" price_band: "$$$ ($20–75 per pen (multi-packs divided by the count), typical US retail, October 2026)" manufacturer: "TaShin Precision (Taiwan)" model: "ECO" sku: "M7445310" url: "https://www.twsbi.com/products/twsbi-eco-clear-fountain-pen" --- # TWSBI ECO: Piston Filler, Ink Capacity & Nib Sizes > The TWSBI ECO is a plastic piston-filling fountain pen from TWSBI, the pen brand of Taiwan's TaShin Precision. It fills only from a bottle, holding up to 1.76 ml per Goulet Pens, and has a screw cap and a steel nib from EF to B or a 1.1 mm stub. Goldspot lists it at 138.8 mm capped. - URL: https://stationerytimes.com/guides/twsbi-eco/ - Category: Pens - Author: Ellis Penhale - Published: 2026-10-20 - Updated: 2026-10-20 ![Side view of a clear TWSBI ECO fountain pen with the cap posted, drawn to scale: 167.5 mm (6.6 in) long posted, with the piston rod visible through the clear barrel and an inset of the steel nib, offered EF to B and 1.1 stub](https://stationerytimes.com/images/raster/twsbi-eco-16x9.png) *The ECO in Clear, posted, to scale, using Goldspot's 167.5 mm figure.* Original drawing (SVG): https://stationerytimes.com/images/twsbi-eco-cover.svg. Drawings © 2026 Stationery Times, reusable with credit under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ## Product facts | Product | Brand | Brand origin | Made in | Material | Released | Price range (typical US retail, October 2026) | |---|---|---|---|---|---|---| | TWSBI ECO Fountain Pen | TWSBI (by TaShin Precision (Taiwan)) | Taiwan | Taiwan | Solid and transparent resin; stainless steel nib | 2015 | $$$: $20–75 per pen (multi-packs divided by the count) | - Made in (TWSBI ECO Fountain Pen): Taiwan. Goldspot's ECO spec sheet says "Made in Taiwan", and Pen Chalet shows "ECO-T Taiwan" engraved on the ECO-T's cap band. TWSBI's own product pages don't print a country of manufacture, and its Taiwanese site, twsbi.com.tw, didn't load for us on October 20, 2026. JetPens says TWSBI nibs are made in Germany. Source: https://goldspot.com/products/twsbi-eco-fountain-pen-in-black ## Key takeaways - Goulet Pens lists the ECO's maximum ink capacity at 1.76 ml; JetPens says 1.5 ml with a basic fill and up to about 1.7 ml. - Goldspot and Goulet list it at 138.8 mm (5.45 in) capped and 167.5 mm (6.6 in) posted, at 21 g. - TWSBI sells it with steel nibs in five widths, EF, F, M, B and a 1.1 mm stub, at US$36.99 in its own store. - It takes no cartridges or converter, and JetPens says it comes with a wrench and silicone grease for maintenance. - Goldspot's spec sheet says made in Taiwan, and Goldspot says TWSBI introduced the ECO in 2015. ## What is the TWSBI ECO? **The TWSBI ECO is a plastic fountain pen with a built-in piston filler and a steel nib, made by Taiwan's TaShin Precision under its TWSBI brand.** Goldspot says TWSBI introduced it in 2015, and The Pen Addict reviewed it in January 2016. TWSBI's own site says TaShin Precision spent more than 50 years as an OEM manufacturer for other brands before selling under its own name, and Dromgoole's dates the brand's launch to 2009. Dromgoole's describes the ECO as bringing the piston filler of TWSBI's Diamond 580 to a lower price. It's one of the four starter fountain pens we cover, with the [LAMY safari](https://stationerytimes.com/guides/lamy-safari/), the [Pilot Metropolitan](https://stationerytimes.com/guides/pilot-metropolitan/) and the [Pilot Kakuno](https://stationerytimes.com/guides/pilot-kakuno/). ## TWSBI ECO specs | Spec | Value | |---|---| | Maker | TaShin Precision (TWSBI), Taiwan | | Type | Piston-filling fountain pen with cap | | Body | Solid and transparent resin; clear and colored versions | | Cap | Screw-on with an inner cap, postable (TWSBI) | | Nib | Steel: EF, F, M, B, 1.1 mm stub (TWSBI) | | Filling | Built-in piston, bottled ink only | | Ink capacity | 1.76 ml max (Goulet); 1.5 ml basic fill, up to about 1.7 ml (JetPens) | | Length capped | 138.8 mm (5.45 in) | | Length uncapped | 131.5 mm (5.18 in) | | Length posted | 167.5 mm (6.6 in) | | Diameter | 12.8 mm barrel, 9.1 mm grip (Goulet) | | Weight | 21 g (13 g body, 8 g cap, per Goulet) | | In the box | Wrench and silicone grease (Goldspot, JetPens) | | Made in | Taiwan (Goldspot) | Lengths are from Goldspot's spec sheet; Goulet lists the same 138.8 mm capped and 167.5 mm posted, with 131.6 mm uncapped. On October 20, 2026 TWSBI's own store listed the ECO at US$36.99, with item codes M7445300 (EF) to M7445340 (1.1 mm stub). ## How does the ECO's piston filler work? **You dip the nib in a bottle and twist the knob at the end of the barrel, which moves a piston that draws ink into the barrel itself.** There's no cartridge or converter, so the whole barrel is the ink reservoir. ![Cutaway of a TWSBI ECO drawn to scale, 131.5 mm uncapped: twist knob, piston rod and seal, ink chamber holding about 1.76 ml, clear grip with feed, and steel nib](https://stationerytimes.com/images/twsbi-eco-piston.svg) *The barrel is the ink tank; the piston seal moves along it.* That's why the capacity is large: Goulet's 1.76 ml is more than four times the 0.4 ml Unsharpen lists for Pilot's CON-40 converter. The trade-off is that you need bottled ink, which also means far more colors. For comparison, the [LAMY Z28 converter](https://stationerytimes.com/guides/lamy-z28-converter/) holds about 0.8 ml, per Unsharpen. The [LAMY 2000](https://stationerytimes.com/guides/lamy-2000/), a gold-nib piston filler, holds about 1.35 ml, per Goulet Pens. JetPens says the wrench and silicone grease in the box are for occasional maintenance of the piston, not something you need on day one. ## Which ECO nib and version should you choose? **Choose EF or F for small handwriting, M or B for a bolder line, and the 1.1 mm stub for italic-style lettering.** | Variant | What changes | |---|---| | ECO (Clear, Black, White and others) | Colors and trim | | Limited editions (e.g. Caffe Bronze) | Seasonal colors | | ECO-T | More pronounced grip; triangular cap and end cap (TWSBI) | | EF / F / M / B / 1.1 stub | Line width | TWSBI doesn't sell a separate ECO nib unit. Pure Pens says a Diamond Mini nib unit also fits the ECO once you remove the nib and feed from the Mini's collar; handle the feed gently. ## How does the ECO compare to other starter fountain pens? **The ECO holds the most ink of the four and has the longest posted length; it's the only one that can't take a cartridge.** | | TWSBI ECO | [LAMY safari](https://stationerytimes.com/guides/lamy-safari/) | [Pilot Metropolitan](https://stationerytimes.com/guides/pilot-metropolitan/) | [Pilot Kakuno](https://stationerytimes.com/guides/pilot-kakuno/) | |---|---|---|---|---| | Filling | Piston, bottled ink only | T10 cartridge or Z28 converter | Pilot cartridge or converter | Pilot cartridge or converter | | Steel nibs | EF, F, M, B, 1.1 stub | EF, F, M, B, LH, italics | F, M, 1.0 stub | EF, F, M | | Capped | 138.8 mm | 139.5 mm | 138 mm | 130.9 mm | | Posted | 167.5 mm | 163.9 mm | 153 mm | 159.7 mm | | Weight | 21.0 g | 17.0 g | 26.0 g | 11.0 g | | Made in | Taiwan | Germany | Japan | Japan | | Price band | $$$ | $$$ | $$$ | $$ | Figures come from each pen's guide. ## Who is the TWSBI ECO for? **It suits writers who already want bottled ink and a big ink supply, and people who like seeing the ink through a clear barrel.** If you'd rather start with cartridges, the [LAMY safari](https://stationerytimes.com/guides/lamy-safari/) or [Pilot Metropolitan](https://stationerytimes.com/guides/pilot-metropolitan/) is simpler. Wet ink needs good paper; see our [Leuchtturm1917 Medium A5](https://stationerytimes.com/guides/leuchtturm1917-a5-notebook/) guide. ## Where is the TWSBI ECO made? **In Taiwan, according to Goldspot's spec sheet.** Pen Chalet's photos show "ECO-T Taiwan" engraved on the ECO-T's cap band, and TWSBI's parent, TaShin Precision, is Taiwanese. TWSBI's own product pages don't print a country of manufacture, and JetPens says TWSBI nibs are made in Germany. ## How much does a TWSBI ECO cost? **The ECO is in our $$$ price band, $20–75 per pen; TWSBI's own store listed it at US$36.99 on October 20, 2026.** It needs a bottle of ink too, since it can't take cartridges. ## Frequently asked questions ### How much ink does the TWSBI ECO hold? Goulet Pens lists the maximum at 1.76 ml. JetPens says 1.5 ml with a basic fill and up to about 1.7 ml with extra steps. That is several times what a typical cartridge converter holds. ### Can you use cartridges in a TWSBI ECO? No. The ECO is a piston filler that fills only from bottled ink, and it doesn't accept cartridges or a converter, according to JetPens. ### What nib sizes does the TWSBI ECO come in? TWSBI sells the ECO with steel nibs in Extra Fine, Fine, Medium and Broad, plus a 1.1 mm stub for italic-style lettering. ### Can you change the nib on a TWSBI ECO? Yes, but TWSBI doesn't sell an ECO nib unit. Pure Pens says a Diamond Mini nib unit also fits the ECO if you pull the nib and feed out of the Mini's collar and move them across; handle the feed gently. ### What is the difference between the TWSBI ECO and ECO-T? TWSBI says the ECO-T has a slightly more pronounced grip section and a triangular cap and end cap. Pen Chalet lists the ECO-T at 1.75 ml with a threaded cap. ### Where is the TWSBI ECO made? In Taiwan, according to Goldspot's spec sheet; the ECO-T's cap band is engraved "Taiwan". TWSBI is the brand of TaShin Precision, a Taiwanese manufacturer. ### What comes in the TWSBI ECO box? JetPens says the pen comes with a wrench and a vial of silicone grease for at-home maintenance of the piston. The pen is sold without ink. ## Sources - [TWSBI: ECO Clear Fountain Pen (official store; nib choices, postable cap, inner cap, item codes, US$36.99)](https://www.twsbi.com/products/twsbi-eco-clear-fountain-pen) - [TWSBI: ECO-T Clear Fountain Pen (more pronounced grip, triangular cap and end cap)](https://www.twsbi.com/products/twsbi-eco-t-clear-fountain-pen) - [TWSBI: About us (TaShin Precision, 50-plus years as an OEM manufacturer)](https://www.twsbi.com/pages/about-us) - [Goldspot: TWSBI ECO fountain pen, Black (dimensions, 21 g, wrench and grease, made in Taiwan)](https://goldspot.com/products/twsbi-eco-fountain-pen-in-black) - [Goldspot: TWSBI ECO fountain pen overview (introduced 2015)](https://goldspot.com/blogs/magazine/twsbi-eco-fountain-pen-overview) - [Goulet Pens: TWSBI ECO fountain pen, Clear (dimensions, 21.0 g, 1.76 ml)](https://www.gouletpens.com/products/twsbi-eco-fountain-pen-clear) - [JetPens: TWSBI ECO Caffe Bronze, Fine (1.5 ml basic fill, up to about 1.7 ml, bottled ink only, wrench and grease)](https://www.jetpens.com/TWSBI-ECO-Caffe-Bronze-Fountain-Pen-Fine-Limited-Edition/pd/42697) - [Pure Pens: TWSBI Diamond Mini replacement nib unit (also fits the ECO once removed from its collar)](https://www.purepens.co.uk/collections/all/products/twsbi-diamond-mini-replacement-nib-unit) - [Pen Chalet: TWSBI ECO-T, Clear (threaded cap, 1.75 ml)](https://www.penchalet.com/fine_pens/fountain_pens/twsbi_eco-t_fountain_pen/Clear/) - [Onlinemantra: TWSBI ECO Heat (screw cap, wrench and grease)](https://www.onlinemantra.in/collections/writing/products/twsbi-eco-heat-ct-fountain-pen) - [Dromgoole's: The history of the TWSBI pen company](https://www.dromgooles.com/blogs/news/twsbi-pen-company) - [The Pen Addict: TWSBI ECO fountain pen review (January 2016)](https://penaddict.com/blog/2016/1/24/twsbi-eco-fountain-pen-review)