Mr. Gasket 5980 Ultra Seal Triangle Collector and Header Muffler Gasket - 2 Piece Set Prevents exhaust leakage between the header and collector flanges Diameter of 1-7/8 Triangle shape with 3-4 bolt holes Bolt circle is 3-3/4" - 3 bolts and 4" - 4 bolts, bolt hole is 7/16 Sold as 2 per set