Good quality rubber check duckbill valve provider from China, visit www.rubberflexiblejoint.com for more information Rubber Duckbill check valve is consist of elastic neoprene rubber and man-made fiber,made by special processing,the shape is similar to the duckbill, so called duckbill valve. Under the condition of no pressure inside, the duck mouth is closed under the action of elastic force,with the increase of internal pressure, the exit of duckbill gradually increases,and the liquid can be discharged at high flow rate.