Threads NPTF per ANSI B1.20.3
Material: ASTM A574 alloy steel.
Pressure plugs are not pipe plugs. Pipe plugs (plumber’s fittings) are limited to pressures of 600 psi, are sealed with a compound, and are made of cast iron with cut threads and protruding square drive.
Pressure plugs that are made to closer tolerances, are generally of higher quality, and almost all have taper threads. Properly made and used, they will seal at pressures to 5000 psi and without a sealing compound (pressure tests are usually at 20,000 psi.) they are often used in hydraulic and pneumatic designs.