Check the listing for details. Shower Floor Drain Backflow Preventer One Way Valve Sewer Core Orange 3 Set. Color: Orange, Condition: New. Listed at 16.29 USD. Description[Material] - The drain backflow preventer is made of ABS and silicone. Silicone is flexible and durable, so there is no need to worry about deformation. It makes full use of the principle of gravity and the properties of silicone to open and close automatically. It opens when exposed to water and closes automatically after drainage.[Anti-odor & Anti-backflow] - Y-shaped inner core prevents the odor generated by sewage from overflowing and also prevents sewage from flowing back. It also allows water to drain easily without worrying about clogging.[Easy to Install] - The drain backflow preventer has a decorative cover, odor-resistant core and sealing plug. First, install the decorative cover on the drain pipe connected to the sink, next insert the anti-odor core, and then install the sealing plug.