Mouse already bought in 2009, I lost recently and am redeemed me the same because the product is fantastic. Precise, comfortable grip, the clip allows not to lose the mouse (usually ...), but also to cut its power when on. Result, I had not yet changed the batteries since late 2009! (Delivered with Duracell). Note that the knob has two positions, one classic before "clicks" and the other "free wheel"! Just press hard on moelette to pass from one to the other position. Useful in some cases. The middle click is therefore located on the small visible blue button easily accessible.