Fountain Pen Converters Explained: Fit, Capacity & Types

Ink capacity of converters, cartridges and built-in fillers as bars to scale, from the 0.4 ml Pilot CON-40 to the 2.37 ml TWSBI VAC700R — Ink capacity · 1 ml = 230 px · makers' and Goulet's figures

Products compared

Product	Brand origin	Made in	Price range
Pilot CON-40 twist converterPilot	Japan	Not stated^*	Price range: $$$5–20 per item
LAMY Z28 twist converterLAMY	Germany	Germany^*	Price range: $$$5–20 per item
Pilot Namiki ink cartridges, 12 per boxPilot	Japan	Not stated^*	Price range: $under $5 per item
LAMY T10 ink cartridges, 5 per boxLAMY	Germany	Germany^*	Price range: $under $5 per item
TWSBI SWIPE fountain pen (cartridge, twist and spring converters in the box)TWSBI	Taiwan	Not stated^*	Price range: $$$$20–75 per item
TWSBI ECO piston-filling fountain penTWSBI	Taiwan	Taiwan^*	Price range: $$$$20–75 per item

Notes on these facts

Pilot CON-40 twist converter: Made by Pilot Corporation (Japan); sold in the US by Pilot Corporation of America. Country of manufacture not stated: Pilot Japan's web catalog entry for the CON-40 lists size, capacity, JAN and price but no country of manufacture, and the Goulet Pens and Amazon listings we read don't give one either. Source.
LAMY Z28 twist converter: Made by C. Josef Lamy GmbH, Heidelberg (part of Mitsubishi Pencil Co., Ltd.). Made in Germany: LAMY's own Z 28 product listing (Ireland storefront) describes it as "Made in Germany", and LAMY's site says Heidelberg has been its only production site since 1930. LAMY's India product page, which gave Germany as the country of origin, has since been taken down. Source.
Pilot Namiki ink cartridges, 12 per box: Made by Pilot Corporation (Japan); sold in the US by Pilot Corporation of America. Country of manufacture not stated: Pilot Japan's web catalog lists ink type, box size, JAN and price for the IRF-12S-B but no country of manufacture, and Goulet Pens' listing doesn't give one either. Pilot is a Japanese company; we didn't find a page naming where the US-packaged Namiki box is filled. Source.
LAMY T10 ink cartridges, 5 per box: Made by C. Josef Lamy GmbH, Heidelberg (part of Mitsubishi Pencil Co., Ltd.). Made in Germany: LAMY's German quality page says it makes nearly all components in-house in Heidelberg, naming the LAMY ink cartridges, and its German ink guide says all LAMY inks are "Made in Germany" at the Heidelberg works. Source.
TWSBI SWIPE fountain pen (cartridge, twist and spring converters in the box): Made by TaShin Precision (Taiwan). Country of manufacture not stated: TWSBI's US store and Goulet Pens' SWIPE listing don't print a country of manufacture, and TWSBI's Taiwanese site, twsbi.com.tw, refused our connection on October 22, 2026. Goldspot says the steel nib is made by JOWO in Germany. TWSBI is a Taiwanese brand, and Goldspot labels other TWSBI pens "Made in Taiwan". Source. Released: TWSBI's US store lists the Smoke and Prussian Blue SWIPE from July 15, 2021; The Gentleman Stationer reported the launch on August 3, 2021 as "last week".
TWSBI ECO piston-filling fountain pen: Made by TaShin Precision (Taiwan). Made in 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.
Price bands are typical US retail, checked October 2026. Conversions to US dollars are approximate, at October 2026 rates (US$1 = ¥158 = ₩1,330 = NT$32.5 = CN¥6.7 = SEK 9.9 = DKK 6.7 = ₺49.6 = C$1.41 = A$1.43 = CZK 21.7; €1 = US$1.12; £1 = US$1.32; CHF 1 = US$1.21).

Key takeaways

Pilot's CON-40 holds 0.4 ml and is 60 mm long; LAMY's Z28 holds about 0.8 ml at 72 mm; Goulet measured Sailor's at 0.67 to 0.70 ml and Unsharpen puts Platinum's at about 0.53 ml.
Cartridges hold more than converters: 0.9 ml for a Pilot cartridge, 1.2 ml for Platinum's, 1.25 ml for LAMY's T10 and about 1.2 ml for Sailor's.
Pilot, LAMY, Platinum and Sailor converters are proprietary; Kaweco's Sport and most European pens take standard international cartridges and converters.
Kaweco lists its Mini Converter for the Sport and Liliput at €6.95 (about US$7.80) and its Standard converter at €8.95 (about US$10); Pilot Japan lists the CON-40 at ¥550 (about US$3.50).
A piston or vacuum pen skips the converter: TWSBI's ECO holds up to 1.76 ml and the VAC700R 2.37 ml, per Goulet.

What is a fountain pen converter?

A converter is a small refillable reservoir, usually a twist piston, that plugs into a cartridge pen in place of the cartridge so you can fill from a bottle. It gives a cartridge pen access to every bottled ink, from a Pilot Iroshizuku to a waterproof pigment ink, at the cost of a smaller fill than a cartridge. The Pilot CON-40 and LAMY Z28 are the two most-bought examples.

Twist (piston): a knob turns a screw that pulls a piston back. The CON-40, Z28, Platinum, Sailor and Kaweco converters all work this way.
Squeeze: a metal bar presses a rubber sac. Pilot’s older CON-20 is one; they hold less and wear out.
Spring: a sprung plunger you press and release, as TWSBI packs with the SWIPE. Fast, with a large fill.

Which converter fits which pen?

Each of the big Japanese and German makers uses its own fitting, so buy the converter from the pen’s maker; European pens built on the standard international cartridge take any standard international converter. Fit is set by the mouth of the section, and a wrong converter either won’t seat or will leak.

Pen maker	Converter	Capacity	Also takes	Band
Pilot, Namiki	CON-40 (twist); CON-70 (push, larger pens)	0.4 ml (Pilot)	Pilot cartridges, 0.9 ml	$$ ($5–20)
LAMY (except 2000)	Z28 (plastic pens, with lugs); Z27 (metal pens)	About 0.8 ml (Goulet)	T10 cartridges, 1.25 ml	$$
Platinum	Platinum converter	About 0.53 ml (Unsharpen)	Platinum cartridges, 1.2 ml; adapter for international	$$
Sailor	Sailor converter	0.67–0.70 ml (Goulet)	Sailor cartridges, 1.18–1.21 ml	$$
Kaweco Sport, Liliput	Mini or foldable Mini	Not stated	Short international cartridges	$$
Kaweco Perkeo, Student, others; most European pens	Standard international	Not stated	Long or short international cartridges	$$
TWSBI SWIPE	Twist or spring (in the box)	1.65 ml (Goulet)	Cartridge 1.46 ml; eyedropper 5.64 ml	Included

Pilot’s CON-70 is the bigger push-button converter for its larger pens; Pilot Japan lists both for the Kakuno and E95S, so check the pen’s listing. LAMY’s red Z28 has two guide lugs for the notched grips of the safari, AL-star and vista; the black Z27 has none and fits any pen the Z28 fits.

How much ink does a converter hold?

Between 0.4 and 0.8 ml for most, which is less than the cartridge it replaces. Pilot publishes 0.4 ml for the CON-40, and its Japanese FAQ says a converter that looks half full after that is normal, since it also draws in the air from the feed. Goulet lists about 0.8 ml for the Z28 and measured 0.67 to 0.70 ml in Sailor’s; Unsharpen puts Platinum’s at about 0.53 ml.

Cartridges hold 0.9 ml (Pilot), 1.2 ml (Platinum), 1.18 ml (Sailor, measured by Goulet) and 1.25 ml (LAMY T10). TWSBI’s SWIPE is the exception among converter pens at 1.65 ml. A 50 ml bottle gives a Z28 about 62 fills, by LAMY’s arithmetic in our T52 ink guide.

When is a piston or vacuum pen better?

When you fill often and want two to five times the ink without a converter at all. Piston and vacuum pens draw ink into the barrel itself: Goulet lists up to 1.76 ml for the TWSBI ECO, 1.61 ml for the spring-piston TWSBI GO and 2.37 ml for the VAC700R, and Pelikan’s Perch puts the Pelikan M200 piston at about 1.2 ml. None takes a cartridge, so there’s nothing to buy for travel ink.

The trade is cleaning: a converter pulls off for a rinse, while a piston pen flushes by cycling water through the nib. Our cartridges roundup covers the other route, and the ink properties explainer says which inks need the most cleaning.

How do you fill and clean a converter?

Fill with the converter on the pen, nib fully submerged; clean by cycling water the same way until it runs clear. Turn the knob to draw the piston back, push forward a little to expel air and a drop or two, then draw again for a fuller fill. Wipe the nib and the section before capping.

To clean, pull the converter off and flush it and the section under a tap, or cycle clean water through the nib in a cup. Pigment inks want this weekly; dye inks when you change colors. A blunt syringe, like the Goulet ink syringes, fills a converter or an empty cartridge directly and skips the nib dip.

Frequently asked questions

Do I need a converter for a fountain pen?

Only to use bottled ink in a cartridge pen. Cartridges work without one, and piston or vacuum pens like the TWSBI ECO fill from a bottle with no converter at all. Many pens, including the Sailor Pro Gear Slim and the TWSBI SWIPE, ship with one in the box.

Which converter fits my fountain pen?

The maker's own, for Pilot, LAMY, Platinum, Sailor, Parker, Cross and Sheaffer pens. Pens built around standard international cartridges, such as Kaweco, Pelikan's cartridge pens, Faber-Castell and Diplomat, take a standard international converter; short pens like the Kaweco Sport need a mini one.

What is a standard international converter?

A converter with the common European cartridge fitting, about 6.4 mm at the mouth, that fits any pen taking standard international cartridges. Kaweco's Standard converter is one; its Mini and foldable Mini are shortened versions for the Sport and Liliput.

What is the ink capacity of a fountain pen converter?

Less than a cartridge. Pilot gives 0.4 ml for the CON-40, Unsharpen about 0.53 ml for Platinum's, Goulet 0.67 to 0.70 ml for Sailor's and 0.8 ml for the LAMY Z28; TWSBI's SWIPE converter holds 1.65 ml. Pilot's cartridge holds 0.9 ml and LAMY's T10 1.25 ml.

How do you fill a fountain pen converter?

With the converter on the pen, dip the nib fully into the bottle and turn the knob to draw the piston back. Turn it forward a little to push out air and a few drops, then draw up again. Wipe the nib and section before capping.

Why does my converter look half empty after filling?

Pilot's Japanese FAQ says the converter also draws in the air inside the feed, so a CON-40 that looks half full after taking up its 0.4 ml is normal. Expel the air and refill, or accept the smaller fill.

Twist, squeeze or spring converter: what is the difference?

Twist converters turn a knob to move a piston and are the usual type. Squeeze converters are a bar you press over a sac, as in Pilot's older CON-20. Spring converters, like the one TWSBI packs with the SWIPE, use a sprung plunger you press and release.

Can you refill a cartridge with a syringe instead?

Yes. A blunt syringe fills an empty cartridge from any bottle, holds more than most converters and costs less; Goulet sells syringe sets for it. Rinse the cartridge first, and replace it when the mouth no longer seals.

Sources (15)

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