12" hub-drum has 6-bolt pattern on 5½" circle. 2½" deep inside for use with 12" x 2" electric or hydraulic brakes (not included). Includes pressed in bearing races. Pilot diameter is 3.63", flange diameter is 7.5". Please note the following is NOT included. Inner bearing (L-25580), Outer bearing (L-15123), Grease seal (SL-213), Lug Nuts (STN-506) or Dust cap (DC-1520).