Up for sale is a Mercruiser / CMI header to riser gasket. The Mercuiser part number is 27-848254. The outside diameter is 5 inches and the inside diameter is 4 inches. These are new high quality American made gaskets that meet or exceed factory specs and designed to withstand the high temperatures of marine exhaust applications. These are sold each. We ship USPS First Class mail for quick delivery and are easy to track.