1/4 in MNPT L-style Plugs are case hardened steel plated to resist rust and have a working pressure of up to 300 psi. 1/4 in basic flow size with air flow of 32 scfm. 1/4 in FNPT L-style Plugs are made of case hardened steel. Maximum working temperature of 300 psi. Plug is plated to resist rust.