These npt threaded plugs do not require washers; tape and thread sealant are recommended for threaded fittings. Designed for use with air, water, oil, natural, manufactured, mixed, liquefied petroleum or propane, and LNG air. Carbon steel resistance, ductility at high temperatures, and low magnetic permeability. Carbon steel air fittings, NPT ends for connecting NPT pipes, resistance, can be applied to water, gas, oil and fuel, and pneumatic tools. Colour:Black Material: Carbon Steel Size: NPT1/8inch, NPT1/4inch, NPT3/8inch, NPT1/2inch, NPT3/4 Temperature Range: -65 to 250 ℉ Maximum Pressure: 1000 PSI Groove: Hexagon Package Contents: 20 x 1/8inch NPT Fittings 15 x 1/4inch NPT Fittings 15 x 3/8inch NPT Fittings 10 x 1/2inch NPT Fittings 10 x 3/4inch NPT Fittings Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.