CST2545W (L-TRAC) USB Wired High Performance Trackball, Black - Made in the USA Laser Precision Tracking Rugged Construction made of High Impact ABS Plastic 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