Rolling Wrist Rest, 5"w x 2-1/4"d x 5/8" h, Black, 1/Pack (99504) The difference is in the roll. Allows movement from mouse to keyboard without lifting your wrist. Independent wheel rotation for smooth rolling in any direction. Ergonomically designed to help reduce joint stress. Soft foam padding provides comfort and support. 5"w x 2-1/4"d x 5/8" h. Black. 1/Pack.