The Twsbi Eco fountain pen series comes in EF, F, M, B, Stub1.1 nib choices
 

Pen cap is able to post onto the back of the pen

Piston Filler Fountain pen.
Simply unscrew the end cap, dip into ink, screw back the end cap, and your done! Ready to write!!

Pen cap has an inner cap to insure a perfect seal when stored away. 
Made for the beginner who just wants to try out fountain pens, all the way to the experts. A good everyday worker.

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?)