Rulu USB wireless mouse for Laptop & Desktop (BLACK) Wireless Optical Technology With Low-Battery Indicator ***Long battery life with advanced RF technology Battery Cover Release Button : Changing batteries has never been so easy. With one simple touch of the release button the battery cover is released, making it easy to change the batteries. The mouse with Low-Battery indicator so you will be reminded to change the batteries. Included in this Packing : Mini Optical Wheel Mouse , Mini USB Receiver , User' s Guide