Hedman offers two different styles of header reducers; a 3-Bolt Flange and Ball & Socket design. The 3-Bolt Flange is two flat mating surfaces that use a gasket to provide a leak free joint. The Ball & Socket design provides an air tight seal by design without the need for any gaskets. The Ball & Socket design also provides some mounting flexibilty by not requiring the two joining pipes to be perfectly aligned. All reducers are package with necessary gaskets and hardware.(Above photo shows 3-bolt flange, O2-sensor style reducers.)