What cartridge/converter will work with my TWSBI?Updated 5 days ago

It depends on which model you are asking about. 

The TWSBI ECO, ECO-T, TWSBI 580/580AL/580ALR, Vac 700R, TWSBI Mini, TWSBI Mini AL, TWSBI Vac Mini, TWSBI Classic, TWSBI Kai, and TWSBI Precision are piston fillers. They will not accept a converter or a cartridge.

The TWSBI Swipe will work with the proprietary TWSBI spring-loaded piston converter, a traditional twist piston converter, and TWSBI proprietary ink cartridges.

The TWSBI Go comes with a spring-loaded piston converter, but does not work with cartridges.