This stainless steel replacement nib unit is compatible with the fountain pens listed under Compatible Products. To replace the nib of any compatible pen except the Kaweco Calligraphy, Classic Sport, and Skyline Sport, use your fingertips to grip the top of the old nib and the feed of your pen and unscrew the entire nib unit from the grip section. Grip the nib and feed of the replacement nib unit and screw it into the grip section until it is tight.