Global Innovation The A4Tech BatteryFREE Wireless Optical Mouse does not need the battery to keep powered on. It works with its partner - the Ingenious Mouse Pad. The Mouse Pad transfers instant & constant power to the mouse as a replacement of batteries. This is we so called: The Electromagnetic Induction Technology. Mouse High Optical Precision Resolution Package Content Wireless Battery Free Optical Mouse RFID-Mouse Pad Users Guide Product Dimension Mouse: 4.45"(L) x 2.44"(W) x 1.38"(H) Mouse Weight: 0.17 Ib. Mouse Pad Weight: 0.40 Ib. Mouse Pad:6.9"(L) x 9.8"(W) X 0.6"(H) Package Weight: 0.95 Ib. Windows®Me/2000/XP/2003 USB Port IBM or Compatible Systems