Microsoft Wireless Mobile Mouse 3500 - Storm Gray Metallic BlueTrack Technology - Works on more surfaces than optical or laser technology. Nano Transceiver - Leave it plugged in your notebook when you're on the go. The mouse has its own on/off switch. Up to 8 months battery life - Power status indicator lets you know when your battery runs low. Comfort - Designed by ergonomic experts for comfort in either hand.