TWSBI Kai Fountain Pen - Premium Writing Instrument for Calligraphy, Journaling & Note Taking - Smooth Ink Flow & Comfortable Grip - Ideal for Students, Professionals & Pen Enthusiasts

Piston Filler Type fountain pen. Simply twist the end knob open and closed to fill the pen with ink. 

Acrylic cap, grip, body, end cap. 
RoseGold plated nib, clip, rings 
Limited Run, Special Edition

Comes in EF, F, M, B nib sizes

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