The IBM Space Saver Keyboard (not to be confused with the IBM Space Saving Keyboard or SSK) was the discrete desktop and server environment adaptation of the IBM Personal System/2 L40SX laptop's Model M3-based buckling sleeves keyboard assembly. The Model M4 is a straight adaptation of that assembly, featuring the same layout but available with beige or black case colour. M4s were originally produced by Lexmark and Key Tronic, however, Unicomp continued selling M4s until 2010. Unicomp's internal codename for the M4 family was "Surf".