Micro precision scroll wheel: Faster, easier web navigation plus advanced optical sensor for smooth tracking on more surfaces, USB receiver is stored inside the mouse where the batteries are located Extended battery life: Go for upto three years without a battery change (battery life may vary based on user and computing conditions) Compact comfort in cool colors: Ergonomic shape, soft rubber grips and great style that's easy to take anywhere Multi device wireless receiver: Tiny unifying receiver connects up to six unifying compatible devices; Mouse dimensions (height x width x depth) 4 x 2.2 x 1.5 inches; Receiver dimensions (height x width x depth) 0.5 x 0.7 x 0.2 inches For windows and MAC computers: Works with windows xp, vista, 7 and MAC OS x 10.5 or later