Sealing ring fits around inside rim of cover and forms a pressure tight seal between cover and body during cooking. Fits Presto pressure cookers Mfg. Nos. 803B, 833, C301A, C301B 3 qt., 804, 804B, C401A, C401B, PSC4 4 qt., C601A, C603A, PCS6 6 quart. Includes rubber automatic air vent.