TWSBI transparent and blue piston filler fountain pen.
To fill with ink: unscrew the end cap, immerse the nib and feed into ink, screw back the end cap, clean ink residue from nib and section.
Nib are available in EF, F, M, B and Stub1.1
Pen cap will post onto the back of the pen.
Pen cap has an inner cap to insure a perfect seal to keep the nib from drying out when not in use.