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 up to 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 For Windows and Mac computers: Works with Windows XP, Vista, 7 and Mac OS X 10.5 or later Receiver Dimensions (HxWxD): 0.57in (14.4mm) x 0.74in (18.7mm) x 0.24in (6.1mm); Receiver Weight: 0.06oz (1.8g)