The Evoluent Vertical Mouse 4 has a uniquely patented contoured upright design which transforms the traditional palm down mousing position to a vertical "handshake" position which is more comfortable for many users. This mouse has a large lip along the bottom of the mouse top revent the pinky finger from dragging on the desk, and contouring which provides comfort, reduced grip force and exceptional control. Performance driven improvements include an instantly accessible pointer speed control button on the side of the mouse allowing the user to select between Extra Low, Low, Medium and High, giving users the ability to select the degree of precision they require for each task. An additional thumb button can also be assigned once a driver is installed. The Vertical Mouse 4 comes in a standard sizes in both right(VM4R) and left (VM4L) handed corded versions in a dark grey housing with silver buttons. A small version of this mouse is also available in a right handed corded model (VM4S), and is easily distinguished as it has a black housing with purple buttons. The small models are suitable for people with hands which are shorter than 7" (17.8 cm)long from the tip of the middle finger to the wrist crease, standard models are for hands longer than 7" (17.8 cm)