HW HAMWOO Solid Brass Air Fitings, Female Coupling Set is used for connecting to various pipes, airlines, air hoses, air tools and air compressors. These couplings are also called brass pipe fittings, brass air line fittings, quick connect air hose fittings, air tool fittings or air compressor fittings. They are made of a solid brass that is durable and resistant to corrosion and long-lasting. The coupling features two 1/4'-18NPT female thread on both ends for connecting two 1/4" male NPT threaded pneumatic parts together. The hex design is perfect for easy wrench installations. It is interchangeable with most air tool fittings. Teflon tape must be used with all fittings to achieve maximum performance.