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TWSBI Range Guide

Most TWSBI pens are a bit different to most others. With most pen brands, their fountain pens all use cartridges or converters, maybe with a piston-filler at the top of the range. But not TWSBI, so a little guide might help you choose the right TWSBI for you.

Common Features

Most of TWSBI’s line-up of pens have clear barrels. Not everyone likes this, but for a lot of fountain pen fans, being able to see the ink inside, to watch it making its way through the pen, and know you’re never going to run out unexpectedly, is part of the fun.

Unlike most other brands, almost all TWSBI pens can’t use cartridges. Again, for some people, that’s a limitation. But for those who prefer bottled ink, these pens can hold more than a cartridge or converter filled pen can - more ink means more writing, more drawing, before having to stop and fill up again. If you use your pens a lot, it can make a real difference, letting you spend more time actually using them, less time refilling.

The Diamonds

TWSBI Diamond Mini Fountain Pen - white and rose goldThe Diamond 580 and Diamond Mini are, as the names suggest, closely related. They’re both piston-filled pens, making them fairly familiar to anyone who is used to converter-filled pens. Wind the piston down, dip the nib into the ink, and wind the piston back up to fill the pen. The difference is in the size - just as you’d assume, the Mini is smaller. For a small pen, though, it does hold quite a bit of ink, but not as much as its larger sibling.

They also have another little trick - if you add the TWSBI Diamond 50 ink bottle, they can fill up even more cleanly and conveniently, by removing their nib units to fill up from the cleverly-designed bottle. The tube inside the bottle lets them suck up the ink down to the final drops too, reducing ink wastage.

The Vacs

TWSBI Vac-filler, connected to the Vac20A ink bottleIn a similar way to the Diamond pens, the Vac 700 and Vac Mini are similar, with the Mini being a bit smaller, but again, both have a high capacity for ink - even more so than the Diamond models. But this comes at the cost of being a bit less familiar to most people. They’re not difficult to use, but if you’re only familiar with converter or piston-filled pens, they just work a little differently.

To fill them, unscrew the blind cap and pull the ‘piston’ up to the top. Dip the nib into the ink, and push the piston all the way down again. Any remaining ink will be pushed out of the pen on the down-stroke, so if there’s ink you don’t want mixing into the current bottle, empty or even clean the pen out first. Ink should fill the pen pretty much completely, pulled in by the vacuum created by the piston pushing back down.

Screw the blind cap back down, and you can start using the pen.

The bit that most often catches people out, though, comes after filling. Once the blind cap is screwed down, it’s sealed off the ink from getting to the nib unit. The ink already in there is enough to write for a little while, but at some point, you’ll need to unscrew the blind cap, and maybe pull the piston up just a very small amount, to let more ink out.

But why would you want that extra trouble? Well, it mainly makes these pens very safe from leaking. Because they’re sealed off when you’re not using them, even if a leak happens, it can only be a very small amount. And it makes them much safer to take on an aeroplane, where the pressure can cause most fountain pens to leak - keep that piston screwed down, and the ink is held in place in the barrel. Open carefully with the tip up, to let the pressure equalise, once there’s no ink left in the feed, and you should be fairly safe to let some more ink into the feed to coutinue using the pen.

Another similarity to the Diamond pens is that there’s a special little ink bottle to go with the Vac pens. The Vac 20A ink bottle can screw onto the Vac pens, giving them a good complete fill, anywhere - coupled with their huge ink capacities, these pens can really keep going!

TWSBI Eco fountain pen, special edition caffe bronzeEco

The name might bring environmental concerns to mind, and a pen that can be refilled thousands of times does seem to justify that, but the ‘Eco’ is actually short for ‘Economical’. It’s basically a piston-filled fountain pen at a super-low price. Similar in most ways to the Diamond pens, the Eco is a bit simpler in construction, making it cheaper to buy, while having most of the same functionality.


TWSBI Go Fountain PenThe GO is a super fast pen to fill. It’s a piston filler, like the Diamond pens, but rather than the usual ‘wind up, wind down’ mechanism, the piston is pushed to the top by a spring, so you just push down and let go. The barrel has to be removed to access the mechanism, but that’s quick and easy to do. It does give it a smaller ink capacity for the size of the pen, but still much bigger than most pens.

Some people will find the big visible spring isn’t to their taste - the mechanism is very much on display, and looks more functional than pretty, but a lot of fountain pen geeks find that very functional style rather appealing.


The Swipe is the TWSBI pen for people who like the TWSBI style, but want the convenience of a cartridge/converter filler. It can use standard cartridges, or standard converters. TWSBI also make a choice of two different converters to go with it, which are a bit bigger than standard ones - only for use in the Swipe, they give you a bigger ink capacity than most pens have with a converter. And you can choose from the usual ‘wind up, wind down’ piston converter or a spring-loaded one that works very much like the TWSBI GO.

TWSBI Precision Fountain PenPrecision

In some ways, the most non-TWSBI-like TWSBI pens, the Precision gets its styling from draughting-style mechanical pencils. Along with the classic pencils, though TWSBI have a matching piston-filled fountain pen, with hexagonal aluminium barrel and a handy little ink window.


The TWSBI Classic and TWSBI Kai are both piston-filled pens with a more traditional look to them - either for TWSBI fans who want something a bit less unusual for when they don’t their pen to stand out quite as much, or for people who might not consider TWSBI usually, because they just don’t like the unusual way they look.


Along with the cleverly-designed ink bottles we’ve already mentioned, for easier filling of their pens to the last drop, TWSBI also make their own inks and cartridges, with some very pretty bottles. Spare nib units are available for many of their pens too. And the TWSBI Pipe fits onto their Diamond pens or many standard converters, helping them to pick up the last drops of ink that you just can’t reach otherwise.


You can’t go far wrong with any TWSBI pens, really. The only ones we’d advise beginners to at least think carefully about are the Vac pens - the lock-out mechanism is a new thing to get used to, probably not the best first experience for a fountain pen, but great if that’s what you know you want. If you’re on a budget, the Eco is great value - it’s most of the features you’d want from a TWSBI, at a bargain price. And the Diamond pens are high quality piston-filled pens, still at a price way lower than most similar pens.

A Little Word on Cracking

If you’ve looked into TWSBI, you may have heard about cracking barrels. It can happen, as it can with any plastic pens, but it’s not as common as you might think from some things we’ve seen. We get very few cases, and they’re usually following people disassembling pens and over-tightening when reassembling. Avoid that, and it’s unlikely you’ll have any problems - and TWSBI are pretty good about helping with the occasional problems too.

Some early models were a bit more troublesome, and the rumour mill keeps grinding on!