Mr. Gasket Package Performance Collector Gasket is designed to prevent exhaust leakage between the header and collector flanges. The triangle collector gaskets are made from a compressed fiber laminate that is heat and tear-resistant. The style of the collector is 3 bolt holes. The inside diameter of the collector gasket is 3-1/2. Bolt circle measures is 4-7/16 and the size of the bolt hole is 3/8.