Illustrate: It's aluminum and PP-R material band,one connected to pipe or elbow,another one connected whorl. Features:1) size:20*1/2, 25*3/4, 32*1a stndard for choicing. 2)Rust , leakproof , defroming and airproof difficult, what is using comprehensive. 3)Corrosive, fungus and germs stressing.