LM-820WC Wireless Computer Optical Mouse with Charger Key Specifications/Special Features: Totally wireless freedom 27MHz digital radio technology One-channel 256 ID to avoid interference 256 changeable link IDs Mouse size: 118 x 60 x 39mm Resolultion: 800 dpi Operation distance: 1.5 meters AAA size Ni-MH rechargeble x 2