TWSBI Diamond Mini Classic Fountain Pen

Piston filler type fountain pen.

Comes in EF, F, M, B, stub1.1

Roughly the same height as an iPhone when capped and stored away

Slightly longer when cap is posted on the pen. (perfect length for writing when cap is  posted on the back)

About 1 inch shorter than a Diamond 580 fountain pen. 

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?)