Type This nib will fit any Sheaffer configured to accept the Imperial-era screw-in nib units  Filling System  The nib is intended for pens which accepted Sheaffer converters and  cartridges. It will not work in a touchdown filling...

Type  Fountain Pen nibs which fit the high-ens Sheaffer Imperial pens of the 1960s thru the 1990s. Product Name  Imperial V-Inlay nibs. This nib is found on Imperial 550s, 444XG, 440XG as well as the later versions of the metal...

Type Fountain Pen nibs which fit the mid-range Sheaffer Imperial pens of the 1960s-70s Product Name We call them "Quasi-Imperial" because they are similar to the higher end Imperial nibs of the same era and in fact are compatible with the higher end pens...