The Diamond Mini comes with a benchmark piston ink-filling mechanism. It's clear and comes with all detachable parts. The pen is very nicely made. It feels solid and of high quality. The nib is smooth with a little feedback. It's roughly the same height as an iPhone when capped, and it's roughly 1 inch shorter than a Diamond 580 fountain pen.
TWSBI Diamond Mini Fountain Pen White Rose Gold II - Stub 1.1
TWSBI Mini AL Fountain Pen - Silver - The Goulet Pen Company
TWSBI Diamond Mini AL Gold Fountain Pen - Fine Nib
TWSBI Diamond Mini AL Blue Fountain Pen Review — The Pen Addict
The TWSBI Diamond Mini
TWSBI Diamond Mini AL Gold Fountain Pen - Hearty Pens
TWSBI Diamond Mini AL Gold Fountain Pen - Fine Nib
TWSBI Mini Fountain Pen in Classic Review –
Fountain Pen Review: TWSBI Mini AL
TWSBI Diamond Mini Review, Rose Gold & AL
Fountain Pen Review: TWSBI Diamond Mini AL Grape - Limited Edition