Wood Hub Wheel Brush, 1 Row, Upright, Overall diameter 3 1/8" Wood Hub Wheel Brush Style 1A, 1 Row, Upright, Overall diameter 3 1/8" 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 7/8", Trim length is 5/8". Bristle tufts are "staple-set" into wood hubs to remain securely fastened.