Prevent seawater from entering the exhaust port when stopping, slowly moving or retreating Includes: Stainless Steel Clamp Suitable for exhaust pipes with an outside diameter of 4 inches. Pack of 2 exhaust guard covers with clamps Replaces Part #s 18-4457,12644A 12644A1 12644Q01, 9-44001,89250 Suitable for exhaust pipes with an outside diameter of 4 inches.