Duckbill check valves, widely used in the demanding applications of many industries, are precision-molded, one-piece elastomeric valves that provide reliable backflow prevention at low pressure differentials. Duckbill check valves allow free flow with positive differential pressure. With negative differential pressure, backflow is checked. Pressure drop across the valve is a feature unique to duckbill check valves. They can be designed to operate in a few millimeters (inches) of water to several hundred kpa (psi), depending on valve size, geometry and compound characteristics. Duckbill check valves are also designed to start functioning at specific opening and closing pressure ranges, depending on your specifications. •normally open one-way check valves •prevents backflow leakage when minimal backpressure is applied •can be installed easily into hole and sealed by compressing flange Duckbill check valve features: Reliable backflow prevention 100% elastomeric construction eliminates maintenance Will not corrode, warp or freeze open or shut 1”-2” cracking pressure, low head loss Curved bill enhances sealing around debris Custom built for each application based on pressure and flow conditions Available in diameters from 1/2" (12mm) to 96” (2400mm) Note: 1. The inner diameters are matched to the pipe outer diameter on which installed. 2. The weight is approximate. 3. The dimensions are not integrated in the above table, contact liangda for more information. 4. We can make duckbill valves with any dimensions rubber flange available as per requirement. 5. Pcs are the number of half part of the clamps. 6. The usual material of the clamp is stainless steel 304, other material availble upon request. 7. Duckbill valves of dimensions in the above table are available in inventory. Any other dimensions and designs available upon request. Plastic bags , wooden box , or as requested