BrassCraft® 3/8 in OD compression nut is machined from brass. Compression fittings are ideal for use in plumbing, instrumentation, hydraulic and pneumatic systems (gasoline, grease, oil, potable and non-potable water, vacuum and air lines). Can be used to install copper, aluminum or plastic tubing. Not recommended for use with steel tubing. BrassCraft® Tube Nut, Series: 61 Series, Fitting/Connector Type: Nut, 3/8 in Nominal, Compression, 0.032 in Thickness, 5/8 in Hex, 0.42 in Length, 200 psi, -65 to 250 deg F, Brass, Rough, 0.382 in ID, Domestic