4-1/2" Brake Drum With Flange, machined on the outside for a band brake. Fits our Tristar wheels. Has a standard 6 bolt pattern for our aluminum split sprockets. The three bolt patterns are as follows: 3 holes (5/16") on a 3.75" Bolt Circle4 holes (1/4") on a 3.75" Bolt Circle4 holes (1/4") on on a 3.228" Bolt Circle (these holes are a bit differently spaced to accommodate the four holes on the mini-hubs AZ_2561 / AZ_2568 / AZ_2565)