4 1/2" Brake Drum with mounting flange. Each drum is designed to fit around the brake drum housing and stop your kart during operation.
The flange is made with a 2 1/8" center bore to fit around the brake drum and axle assembly. In addition, there are 3 sets of mounting holes for the internal brake drum or components.
A 3 and 4 hole pattern feature a 3.75" diameter bolt circle, with a 4-hole 3.228 bolt circle, which matches the Azusa Mini-Hub perfectly.