trust quality: dutch design and 30+ years of experience in serving over 100 million satisfied customers optical sensor for accurate control. 2 extra thumb buttons: browser back/next. ultimate ergonomic design for longlasting & comfortable usage. rubber coated surface for perfect grip. speed select button (800/1200/1600 dpi). storable micro usb receiver. trust quality: dutch design and 30+ years of experience in serving over 100 million satisfied customers note : in case of wireless mouse, the usb receiver will be provided inside or along with the mouse optical sensor for accurate control. 2 extra thumb buttons: browser back/next. ultimate ergonomic design for longlasting & comfortable usage. rubber coated surface for perfect grip.