IMAGE Wireless Finger HandHeld USB Trackball Mouse for Laptops Desktops Plug and Play, easy to install;Wireless, With trackball, cool Off table and without limitation of operational space; Scrolling function can be controlled simply by your thumb;USB 2.0 interface, plug and play, no software required. Special design, can avoid the harm on your wrist and muscle, greatly reduces discomfort for Arthritis and CTS suffers; Easy to use - left or right hand, or cradled between both;Ideal for both laptops and desktops Place end of index or middle finger on trigger button & thumb on roller ball