Up for sale is a set of exhaust riser gaskets. These will fit Gale Banks Harman Marine and other aluminum exhaust manifolds with 3/8 inch studs. The outside diameter is 5 inches, the inside diameter is 3 inches and the holes are 3/8 inches. These also can be used on manifolds with 5/16 inch studs. We have these custom made for us from HTX-900 material and when installed properly they will not leak. We ship USPS First Class Mail for quick delivery and up to date tracking.