Wood Hub Wheel Brush, 3 Rows, Upright, Overall diameter 2 3/4" Wood Hub Wheel Brush, 3 Row, Upright, Overall diameter 2 3/4" consists of Chungking bristles mounted into a hardwood hub with 1/4" arbor hole to fit tapered spindles of polishing motors. Wooden Hub diameter is 1 3/8", Trim length is 11/16". Bristle tufts are "staple-set" into wood hubs to remain securely fastened.