Compiled from 6 sources; we haven't tested this product ourselves yet. How we research
Quick answer
The TWSBI Vac20A is a 20 ml plastic travel ink bottle with a three-part cap. Screw a TWSBI Vac700R or Vac Mini into it, flip it and pump, and the pen fills completely instead of about two-thirds. Remove the big cap and any fountain pen can dip in. It comes in five colors, sold empty, in our $$ band.
On this page12 sections
Three caps, three uses: Vac Mini, Vac700, and an open inkwell for any pen.
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Notes on these facts
Made by TaShin Precision (Taiwan). Made in Taiwan: The Journal Shop's spec list says "Country of Origin: Taiwan". TWSBI's own store page (read October 22, 2026) doesn't print a country, and we found no Taiwanese-language TWSBI page for it. Source. Price: example listing.
Price bands are typical US retail, checked October 2026.
Key takeaways
TWSBI lists the Vac20A at 20 ml, in Blue, Black, Green, Red and Orange (item codes M7444540 to M7444580).
JetPens says a Vac700 or Vac Mini normally fills about two-thirds; the Vac20A fills it to maximum capacity.
The cap has three levels: one for the Vac Mini, one for the Vac700 and an open bottle for all pens, per TWSBI.
The cap also fits TWSBI's Diamond 50 ink bottle, according to TWSBI.
JetPens' Red Vac20A had 13 reviews and Goulet's Green 13 reviews on October 22, 2026.
What is the TWSBI Vac20A?
It’s TWSBI’s 20 ml travel inkwell, designed so its vacuum-filling pens can fill completely. TWSBI sells it empty in five colors; you pour in your own ink.
It’s a small accessory with a loyal following among TWSBI owners: on October 22, 2026 the Red version had 13 reviews at JetPens and the Green 13 at Goulet Pens.
On October 22, 2026, TWSBI’s own store listed each color at US$16.99.
Why does a Vac700R need the Vac20A?
Because a vacuum filler dipped in an open bottle takes in air too. JetPens says the Vac700 and Vac Mini normally fill about two-thirds full that way.
Screwed into the Vac20A, the pen and bottle form a seal. Turn them over so ink pools around the nib, pump, and the chamber fills to its maximum. See our TWSBI VAC700R guide for the pen itself.
How do you use the TWSBI Vac20A?
Remove the right cap, screw the pen in, flip, pump, flip back. JetPens gives the steps in this order:
Unscrew the small colored cap for a Vac Mini, or the colored cap and the grey adapter for a Vac700.
Uncap the pen and screw it into the bottle, holding the bottle upright.
Turn pen and bottle upside down so ink pools around the nib.
Unscrew the piston knob and pump the piston once or twice.
Turn them upright, unscrew the pen, recap the bottle and wipe the nib.
The fill in three panels, following JetPens' instructions.
Can other fountain pens use the Vac20A?
Yes, as a plain inkwell. TWSBI says the lower cap level is “made for ALL fountain pens”: take off the big cap and dip any pen, converter or syringe into the open bottle.
The screw-in trick only works with the Vac Mini and Vac700 threads. A TWSBI ECO, for example, fills from the open bottle like any piston pen. For bottles without a well like this, a separate cup such as the Ink Miser Ink-Shot does the same job.
What color should you pick?
Pick the color that matches the ink you’ll keep in it. The bottle itself is clear; only the small Vac Mini cap is colored, so a few bottles in different colors make it easy to tell inks apart.
TWSBI says the cap also swaps with the Diamond 50 bottle’s cap.
How many fills does 20 ml give?
Roughly eight full fills of a Vac700R, if you fill the bottle to the top. Goulet Pens measures the VAC700R’s maximum at 2.37 ml, and 20 ml divided by 2.37 ml is about 8.4.
In practice you’ll get fewer, because the pen needs ink pooled around the nib to pump, and the last few millilitres in the bottle won’t cover it. Top up the bottle before it runs low.
Should you buy the Vac20A or the Diamond 50?
Buy the Vac20A if you own a Vac700R or Vac Mini, or want a small bottle for travel; buy the Diamond 50 for a larger desk inkwell. TWSBI’s store listed the Diamond 50 at US$28.99 on October 22, 2026, against US$16.99 for the Vac20A.
Only the Vac20A has the Vac Mini cap and the Vac700 adapter, and TWSBI says the two bottles’ caps interchange.
Where is the TWSBI Vac20A made?
In Taiwan, according to The Journal Shop’s spec list. TWSBI’s own store page doesn’t print a country, but TWSBI is the brand of TaShin Precision, a Taiwanese maker.
Frequently asked questions
Does the TWSBI Vac20A come with ink?
No. It's sold empty; JetPens says ink isn't included, so decant your own bottled ink into it.
Does the Vac20A work with the TWSBI ECO or Diamond 580?
Not as a screw-on filler: the threaded caps are made for the Vac Mini and Vac700. With the big cap removed it's an ordinary 20 ml inkwell any fountain pen can dip into.
Why doesn't my Vac700R fill all the way?
Dipped in an open bottle, a vacuum filler pulls in air as well as ink; JetPens says it fills about two-thirds. Screwed into a Vac20A and flipped, it seals and fills completely.
What's the difference between the Vac20A and the Diamond 50?
The Diamond 50 is TWSBI's larger ink bottle; the Vac20A holds 20 ml and is sized for travel. TWSBI says their caps are interchangeable.
Can I travel with ink in a Vac20A?
That's what TWSBI calls it: a travel-size bottle. Keep it upright and bagged, since pressure changes in flight can push ink past any screw cap.
What colors does the Vac20A come in?
Blue, Black, Green, Red and Orange. The color is on the small Vac Mini cap; the bottle itself is clear.
