Sealand / Dometic (385347802),  1 1/2" DuckBill Valves used for all S-Series and T-series Vacuum Pumps.

4  SeaLand / Dometic DuckBill Valves needed to rebuild an S-Series pump.

Only 2  DuckBill Valves required for T-Series pump (note - T-Series pump nipples are left handed threads)