The Camco RV 4" x 3" Sewer Hose Seal is a sponge ring that works with either the gray water seal or directly on sewer hose for an odor-proof connection to dump station.• Connects directly on RV sewer hose for an odor proof connection to dump station• Works with the gray water seal• 4" x 3" dia. Also works with the gray water seal Measures 4"" x 3"" | Camco 4" x 3" Sewer Hose Seal in Grey