... quality garantee 2) specific certificate3) good quality and competetive priceRubber duckbill check valve size standards:Mounting ... you can use five years, even as long as 10 years, but the proposed one- ... in water pressure automatically turn on and off, safe and reliable, no noise, no need ... ) Anti-corrosion, adaptability, and long service life. 5) A wide range of sizes and nominal diameter DN50-DN2400. ...