It can be operated in various ways to long-term use without harm to wrist or muscleNo limitation of operational spaceAvoid sitting closely to the monitor and reduce the harm of radiation and eye fatiguePlug and play ,no software requiredFits left and right handed usersIt is ideal for laptop users.Specifications:Compatible with Windows95/ 98/ 2000/ / XP/ NTUnit Dimensions: 3.15 x 2.05 x 1.97 inches (8 x 5.2 x 5cm)USB Cord Length: 73inches (186cm)Color : BlackHow to Use:Put your or middle finger into the hole of this mouse.Control the ball for moving cursor and press the right and left button with your thumbWhen using ""Drag and Go"" function, press the button in the hole of the mouse that has the same function as the left button of the common mouseUse the left button to lock the screen and then you can control the ball to your screen freelyMaterial:PVCsilicone Package Includes:1 x Hand 4D Usb Mini Trackball MouseNote:Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.