The Model M5-2 is one of two variants of the Enhanced Keyboard featuring an integrated trackball pointing device attachment, along with the M5-1. The M5-2 uses a 25mm trackball placed on the top-left corner of the keyboard case and features eight mouse buttons; two for left and right click and two for left and right stepped-click, with both pairs repeated on the back-side of the trackball module. Unlike the M5-1, the M5-2 has remained in production and continues to be produced by Unicomp as the Unicomp Classic Trackball Keyboard (also previously called "On-The-Ball"). Collectively, the M5s were the last introduced Model M variants to feature a modular SDL connection. However, Unicomp has since moved the M5-2 to a fixed cable design.