All nipples have a weld bead inside and are NPT threaded at both ends. Black nipples are interchangeable with black cast iron or steel. For low-pressure plumbing applications including air, water, oil, natural gas, and steam. Threads conform to ANSI B1.20.1 standards. Material conforms to ASTM A-53 Type E, Grade A standards. Manufacturing conforms to ASTM A-733 standards. Maximum pressure: 150 PSI WOG @ 150 Degrees F, 150 PSI saturated steam.