Cast coupling with female threads is Great for attaching or extending your Male threaded plumbing. Most standard couplings are big bulky castings but these are very sleek and low profile. Threads cut well without burrs. Recommend Teflon tape on the threads for a good seal and cinch it down hard. With proper installation, it connects nicely and solidly with no leaks or imperfections. Resistance to corrosion and applicable medium: water, oil, gas, etc.When purchasing pipe fittings, consider the application.