I have bought over a dozen of these. They work absolutely perfect. They are a great male pipe thread in-line back-flow preventer / check valve. I have these installed between our coffee machines and city water line. If you let them sit too long the spring will end up getting rusty and corroded on you, but if you soak it and clean it out it will be good as new again. It only happened to us once, on a machine we didn't use for several months... but daily use they have no issues.