USB 2.0 Standard Desktop 4 Button Basic Function Mouse with Scroll Wheel. BASIC FUNCTION MOUSE : Typical basic button layout and functions with center scroll wheel. FOUR BUTTON : Fourth button functions as a convenient browser "back/return" button. DESIGN : Comfortable ergonomic design for less hand/wrist discomfort. CORD : 5" cord for maximum reachability. SIZE : 5"L x 2.75"W.