Threaded x socket fittings connect with pipe to transport natural or propane gas, water, steam, and air to residential, construction, and manufacturing applications. Threaded x socket fittings include at least one threaded end and one socket (hub or slip) fitting end. Female threads are on the inside of a fitting. Male threads are on the outside of a fitting and screw into the female threads. Threaded connections include NPT (National Pipe Thread) or BSPT (British Standard Pipe Taper), and use PTFE tape to secure seal. Socket ends require glue or adhesive to secure connection. Uncoated black steel fittings, also called black malleable iron, are made from corrosion-resistant ungalvanized steel with a scaly, dark-colored iron oxide coating. Fittings come in a variety of sizes and shapes.