Wing Sung 3008 Transparent Piston Fountain Pen Set of 4 Pieces , 4 Color Pen Cap The fountain pens nib : Iridium fine nib ( about 0.5 mm ) / Cap : Screw Type Ink : piston fill ink , fit all bottle ink . Please pull the end of the pen out a little, then screw the piston to fill ink Length(Approx): 140 mm ; Weight(Approx): 15 g ; Diameter: 14 mm Package : 4 pieces fountain pens as picture shown , no ink including Please pull the end of the pen out a little, then screw the piston to fill ink . The cap screws on and off over the nub, pulls off or snaps on at the other end.