... , whole rubber structure ,with duch mouth shape ,with character of "Forward flow, reverse Check" new type water drainage product.Depend ... , better performance . D)Resistance to corossion ,aging ,deformation ,with long using life . E)Wide range of size , DN 50--DN3000Application1 ... 401503204727534026527536026550200375197338420325338450325502504752474005204254005604257530056029748Type Rubber Back valve