TWSBI ECO-T Mint Blue Limited Edition Fountain Pen Fine Nib (F)ECO T has a slightly more pronounced grip section; to help with learning correct writing posture for kids, new enthusiast, and anyone who likes a little bit more structure to the grip area. Cap and end cap also has a rotary triangular shape design. 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