Duckbill Valves for E10/S1/S1 Pro Original, Clear #T8D02181-88UOM 1 EACH Details Duckbill Valve: Compatibility: Compatible with eufy Breast Pump E10 S1 S1 Pro. Closed, Anti Blackflow Design: Designed to prevent backflow of breast milk and help direct milk to the bottom of the container, ensuring no loss of suction. The slit on the valve tips remains closed when not pumping. Food Grade Silicone: Made from durable, BPA free, food grade silicone, the duckbill valves are soft, odorless, and skin friendly for both