CST2545-5W (L-Trac) USB Wired Ambidextrous High Performance Laser Ergonomic 5-Button Trackball (Black) - Made in the USA Width 3.75" (9.5cm), Length 6.75" (17.1cm), Height 1.75" (5cm) Ball Size: 2.25" Resolution: User selectable 400, 800, or 1600 counts per inch Made in the USA Buttons: 3 (programmable) + 2 switch jacks (programmable) which allows users to plug in two external buttons (Sold Seperatly - CST S-Button External Switch) for a maximum of 5 buttons