Homemade duckbill valve

Duckbill valves as exhalation valves for double hose regulators are nowadays difficult to obtain.So it stands to reason, selfmade some. After my attempts in 2008 with normal bicycle hose, I recently saw a XXLight hoses in my bike shop. It consists of very thin and flexible rubber. It turned out that its to be the ideal material for the selfmade production of duckbill valves. In conjunction with a bit of Pattex are produced some parts at the kitchen table speedy