This is a 4MB SIMM memory module for the HP LaserJet 4 & 5 series of printers. This module will support the following LaserJet models: 4P, 4MP, 4 Plus, 4M Plus, 4V, 4MV, 5P, 5MP, 5SI, 5SIMX, 6P. It also supports the Color LaserJet series of printers.