... good quality and competetive priceRubber duckbill check valve size standards:Mounting dimensions flange connection to the GB, which is the earliest design ... two years, but in general, at room temperature, and the climate is bad, you can use five years, even as ... no leakage, prevent backflow, the greater the back pressure, the better the effect. 4) Anti-corrosion, adaptability, and long service life. 5) ...