Description[Material] - The backflow preventer is made of PVC, which has high hardness. It is corrosion-resistant and very durable. It makes full use of the principle of gravity to open and close automatically. It opens when exposed to water and closes automatically after drainage.[Anti-odor & Anti-backflow] - It prevents the odor generated by sewage from overflowing and also prevents sewage from flowing back. It has a large-diameter drain outlet and a large drainage volume. It allows water to drain fast without worrying about clogging.[Easy to Install] - It is easy to install, just put the back drain on the outside of the drain pipe and fix it with a clamp. It is a variable diameter design, don't worry about the pipe diameter not matching the backflow preventer exactly.