Works on difficult surfaces like armrests, pant legs, seat cushions & even glass tables ; Terrain Tested Tracking Technology utilizes a blue LED sensor to deliver rock-solid cursor control practically anywhere; 1000dpi sensor ensures an optimum blend of tracking speed & accuracy ; Attractive, ambidextrous design looks great & provides comfort for both left- & right-handed users; System requirements: PC with Windows(R) 98/XP/Vista/7, Mac(R) OS X(R) v10.0 or later & available USB port;