The IBM Space Saver Keyboard with TrackPoint II (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. Compared to the standard Model M4, the M4-1 is a modified design that equips a TrackPoint II pointing stick. These M4-1s were notable for being the first IBM desktop keyboard to feature TrackPoint strain gauge technology and the only Model M to retain such a stick when produced by Unicomp. M4-1s were originally produced by Lexmark and Key Tronic, however, Unicomp continued selling M4-1s until 2008. Unicomp's internal codename for the M4 family was "Surf".