Ergonomic Mice in Right and Left handed versions with assorted sizes. The Contour Ergonomic Mouse is the only mouse that gives left handed users a Perfect Fit. This ergonomic mouse is available in a variety of sizes for both left and right handed users. Right handed sizes are small, medium, large and extra large. Left handed sizes are small, medium and large. All sizes include a PS2/USB adaptor. To establish your personal mouse size, measure the length from the crease of your wrist to the end of your longest finger: Less than 17cm - Small 17cm - 19cm - Medium 19cm - 21cm - Large More than 21cm - Extra Large * (* Not available left handed) •Right hand – 4 versions. •Left hand – 3 versions. •Reduce RSI risks with sculptured elevated buttons, thumb support and elevated wrist support. •Programmable software. •USB and PS/2 connections. •'No-Ball' Optical Mouse.