The ever popular Diamond 580 now withmatte finish, subtile details on the grip and cap. And new aluminum machined grip, connector, and piston rod.

TWSBI Diamond 580, a classic fountain pen with a piston ink-filling system. By fusing the traditional mechanisms of the fountain pen with a modern industrial design, TWSBI has created an eye-catching fountain pen that is simultaneously appreciative of the past and relevant in the present. The Diamond 580 comes with a benchmark ink-filling mechanism and has all detachable parts. TWSBI feels it is important to allow the user to disassemble and reassemble the pen and completely experience the traditional aspects of owning and using a fountain pen. 

• Comes with a medium steel nib
• Grip Diameter: 11.0mm
• Length (Uncapped): 13.0cm
• *Please note : ink is not included 

A quick no brainer guide in choosing nib sizes in an overly complicated fountain pen world:

If you write small, go with an EF
For the normal writer, F is the most popular
If you tend to lean on a bigger font, M will be perfect
B is for statements!! Sign a check in B, write a header in B, do some coloring/shading in B
Stub nibs are italic in writing style (have a special card or invitation to write?