Wood Hub Wheel Brush, 4 Rows, Converging, Overall diameter 3 1/2" Wood Hub Wheel Brush, 4 Rows, Converging, Overall diameter 3 1/2" consists of Chungking bristles mounted into a hardwood hub with 1/4" arbor to fit tapered spindles of polishing motors. Wooden Hub diameter is 1 7/8", Trim length is 13/16". Bristle tufts are "staple-set" into wood hubs to remain securely fastened.