ERGONOMIC DESIGN - handheld trackball mouse wireless can greatly avoide the harm of palm and muscle of your wrist for long time using mouse. ATTENTION: IF YOUR MOUSE IS NOT WORKING WHEN YOU WENT A FEW MINUTES WITHOUT USING IT, PLS KINDLY CLICK TO WAKE IT UP.IF STILL NOT WORKING, PLS CHECK BELOW ISSUES: 1, CHANGE BATTERY AND TRY; OR 2, TURN IT OFF AND ON; OR 3, REMOVE THE USB RECEIVER AND TRY IT. TRACKBALL COMFORT - Ergonomic handheld trackball mouse wireless is a best choose to reduce the chances for Arthritis and suffers. Hold ergonomic handheld trackball mouse wireless in your hand like a trigger and use your thumb to move around. Sculpted shape supports your hand staying in one place, move the cursor without moving your arm.Suitable for both left and right hand - New style, no space limitation, left/right clickers, fit left and right handed users. ADJUSTABLE DPI - ergonomic wireless handheld finger trackball mouse have 800/1200/1400/1600 DPI resolution optical tracking technology that provides higher sensitivity than standard optical mice. handheld trackball mouse wireless have a Sensitive rolling ball and frequency stable 2.4GHz receiver(For wireless mouse, the valid range distance is about 10M, the signal can't go through wall). WIDE APPLICATION - handheld trackball mouse wireless including USB 2.0 interface, plug and play, no software required. Suitable for laptops and desktops, but NOT FOR TABLETS AND CELLPHONES. Compatible with: for XP / VISTA / Win7/ Win10/ Linux / Unix / OS. Wireless mouse, by AAA battery (not included), plug and play. Material: plastic colour: black Package Contents: 2 x Wireless Trackball Mouse 2 x USB Receiver Only the above package content, other products are not included. Note: Light reflection 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.