joywayus 4pcs stainless steel internal hex thread socket pipe plug 1/4"npt male joyway this joyway stainless steel plug has an internal hexagonal head and male national pipe taper (npt) threads for closing off the end of a pipe or fitting. the plug inserts into female pipe and has an internal hexagonal head for increased leverage with a wrench during installation and disassembly. it is made of stainless steel which is high strength and has greater corrosion resistance than brass and has npt threads for creating a tighter seal than straight threads. this fitting meets standards ansi b31.1, ansi b1.20.1, and sae 090109a for quality assurance. pipe fittings are components used for connecting, terminating, controlling flow, and changing the direction of piping in many different industries. when purchasing pipe fittings, consider the application, as this will affect material type, shape, size and required durability. fittings are available threaded or unthreaded, in many shapes, styles, sizes, and schedules (pipe wall thickness).