Kensington Optical Expert Ergonomic Mouse Four button trackball for maximum precision and control. The Kensington Optical Expert is a solid four button trackball that is ideal for those want a heavy smooth running ball that enables precision cursor movement. A light touch on the large trackball is all that is needed to move around the screen. Trackballs are especially good for those who find it difficult to grip a mouse and click at the same time and the optical mechanism means that this mouse needs much less cleaning. The four buttons are all programmable using the MouseWorks software included with the product. The unique scroll ring is a real bonus for those who work with long documents and the rubber grip on the ring makes this very easy to use with your thumb. People who have RSI or similar musculo-skeletal problems can benefit from alternating between an ordinary mouse and the trackball as a means of reducing repetition. The detachable wrist rest provides added comfortand makes this a more ergonomic mouse for both left and right handed users. Features DiamondEye Optical tracking for superior accuracy Award-winning Scroll Ring® for precise fingertip scrolling Exceptional comfort for ultimate productivity Large ball for maximum precision and control Detachable wrist rest cradles hand in comfort Specifications Compatible with Windows®7, Windows® XP, Windows Vista®, and Mac OS® X System Requirements PC running Windows 98 or later with an available USB or PS2 port. Mac® running OS X or later with an available USB Port. Internet connections or CD ROM drives to install the software. Dimensions Housing height is 1.75 5.75"L X 2.5"H X 5.0"W Cord length - 6´ 55 mm is the circumference Price: £92.00 (Excluding VAT at 20%) Quantity: