Caps sealing material threaded in the water sector are produced by material of iron, stainless steel, copper is used to seal threaded outer end of the tube is often called the sealing cap DN15, DN20, DN25, DN32, DN40, DN50, DN65 , DN80, DN100 and external reverse threaded type fitted to the threaded pipe end called plugs 21, 27, 34, 42, 49, 60, 76, 90, 114.