ELECOM M-DT2URBK Wired Trackball Mouse for The Index Finger 8 Button tilt Function, Black ELECOM acquired FCC certification. Comes with both English and Japanese manuals Changing the common sense of index finger operated, index finger operated type USB trackball 'DEFT' With Back/Forward quick navigation buttons. Thumb-operated ball with advanced gaming sensor. For exceptionally smooth tracking Ball diameter size is 2.5mm. Ergonomic design of the thumb ball operation. Left/Right button made by OMRON With Back/Forward quick navigation buttons. With scroll Wheel. Resolution: 750/1500 count (switchable). It is easy to remove the ball, you could clean the hole easy. Simple package