The Model M6-1 was the TrackPoint equipped variant of the Model M6 used throughout the mid-'90s as the standard ThinkPad keyboard. The quality and utility of the Model M6-1 were regarded as a significant factor in the ThinkPad's market success. Whilst initially produced by Lexmark and Key Tronic as a buckling sleeves keyboard, the Model M6-1 was later substituted by scissor-stabilised rubber dome assemblies produced by Acer, Alps, LITE-ON and NMB. These Model M6-1s mostly came with TrackPoint II or III sticks, with some later ones receiving TrackPoint IV with a dedicated scroll button.