... . XH41A XH81,XH41,XH81A,XH41A Rubber Sewage Check Valve (Duck--billed flexible check valve in Spain and Duck--billed Rubber Flat bill ... greater intensity,toughness and tightness .What's more, the valve is free from any repair and maintenance in the view ... treatment .As green environment friendly valve ,it can deal with the difficulty of obstruction by sand ,block, silt and so on. Matching ...