The idea behind the TWSBI Mini fountain pen was to go back to basics and capture the simplicity and elegance of traditional writing instruments. The Mini is a classically styled fountain pen with a piston ink-filling system, smooth-writing steel nib and a screw-on cap. The traditional mechanism of the fountain pen, combined with a modern industrial design, embodies both the past and the present. This pen runs smaller in length than the Diamond 580 or the Classic model of pens. The cap does post, by screwing on the cap onto the barrel.
The TWSBI Mini piston ink-filling system uses only bottled ink and the clear body allows the user to view the level of ink remaining in the pen at all times. The TWSBI Mini fountain pen has all detachable parts, as TWSBI felt that it was important to allow the user to disassemble and reassemble the pen to completely experience the traditional aspects of owning and using a fountain pen.