Npt Thread: 3/4" Npt x 14 Tpi Female (Actual Nominal Thread Size 1-1/16") Inline female NPT coupling fittings are a type of brass pipe fitting that provides a leak-proof connection between two pipes with female National Pipe Thread (NPT) ends. These fittings are designed to be inserted directly into the end of a pipe and secured with a wrench to create a tight seal. The female NPT thread is tapered, allowing for a secure fit that prevents leaks and ensures a reliable connection.