Locknut, 3/8 in Nominal Pipe Size, Brass, C36000, Female NPT, 3/8 in -18, 1,000 psi Maximum Operating Pressure, 1,000 psi Max. Steam Pressure, -65 Degrees to 250 Degrees F Featuring high-impact strength and resistance to mechanical shock and vibration, this PARKER locknut is used with brass pipe fittings that can be used with brass, copper, and iron tubing. Locknut is for use in aggressive and general industrial environments and is compatible with many fluids.