Thrifco Plumbing now offers black iron fittings for use with black malleable iron piping. These fittings are specially designed for use with oil and gas applications. Black iron (also referred to as schedule 40 steel or schedule 40 black pipe) is a durable material that withstands high temperatures and pressures. Nipples do the important job of connecting two fittings that are close to each other. Nipples come pre-cut and pre-threaded, unlike black iron pipe, which must be cut and threaded for each joint. This makes black iron nipples an extremely convenient and time-saving piece of hardware.