Ergonomic Design & Size - The real ergonomic shape fits your hand very well, designed with thumb and finger rest, which keeps your wrist/arm being in nature position and alleviates the strain/pain on your wrist. It fits better for /Men hands, maybe NOT very comfortable for Women/Small hands. (Right-handed) Silent Click - Left and right click is silent (NOTE: other buttons are general), which makes you conveniently work without disturbing others in the evening, or in the library/the coffee house/. Rechargeable & Wireless - Built-in rechargeable Li-battery. This ergonomic mouse lasts about 12-20 under moderate use after fully . The backlight can be separately controlled. It works while charging. 2.4G wireless connection, no wire hassle. 3 Levels & Compatibility - 800/1200/1600 (slow to fast), adjusted via button. Plug and play. Compatible with Windows 8/7/10/Vista/XP/2000, , Linux (NOTE: The side forward/backward button is not recognized on ). Specifications Battery Capacity: 400mA Charging Time: about 2 hours : 800-1200-1600 : 5-million times Compatibility: Windows, Linux, (The forward/backward button is not recognized on ) Colour:Black Material:ABS Size:12.3x8.9x7.2cm Package Contents: 1* wireless mouse 1* USB charging cable 1* English manual Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.