NPT plugs, mild steel black engine oil gallery plug and engine water jacket screw in plugs.

Stainless Steel NPT plugs are also available click here

NPT Thread is not so easy to determine like a normal bolt so use this chart and measure your engine to determine what size you will need. Most engine applications are limited to 1/4, 3/8 and 1/2 inch NPT.

Sometimes NPT threads are referred to as MPT ('Male Pipe Thread'), MNPT, or NPT(M) for male (external) threads. The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, as opposed to parallel/straight thread fittings or compression fittings in which the threads merely hold the pieces together and do not provide the seal. However a clearance remains between the crests and roots of the threads, resulting in a leakage around this spiral. This means that NPT fittings must be made leak free with the aid of thread seal tape or a thread sealant compound - plumbers white tape

There is also a semi-compatible variant called National Pipe Taper Fuel (NPTF), of which our mild steel plugs are. Defined by ANSI B1.20.3, designed to provide a more leak-free seal without the use of teflon tape or other sealant compound. NPTF threads are the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.