Ultra Seal Collector & Header Muffler Gaskets. Ultra Seal Collector & Header Muffler Gaskets; Triangle; 3 Bolt Holes; 3 in. Dia.; 3 7/8 in. Bolt Circle; 3/8 in. Bolt Hole; 2 pc.;. Now an important part of Holley Performance, Mr. Gasket continues to expand application coverage with more and more new products for race cars and muscle cars alike.