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.
About TWSBI:
TWSBI 三文堂 (San Wen Tong) is one of our earliest collection even before the store. TWSBI started as an OEM manufacturer for different western brands, and around 2009, they decided to start their own brand. With 50 years of experience in pen making, they took to fountain pen forums and gather users’ feedback. It was said that Pelican M800 was the model they were inspired. Most of their pens are transparent, so it’s really fun to see the ink color and it lasts for a very long time.
The name 三文堂 (San Wen Tong) comes from the Hall of the Three Rare Treasures, created by Emperor Qianlong as a memorial to three great masterpieces of Chinese calligraphy. The initials of the name “San Wen Tong” was reversed and thus turned into "TWS". The last letters "Bi" was added with its literal meaning of "writing instruments" in Chinese. Thus combining the two segments, creating TWSBI.