This part is a 1 1/2" MPT Threaded plug that is used in Swimming Pools to block off the 1 1/2" Threaded returns when winterizing to stop water from being in the plumbing system and used on some Sand...
This item is a 1/4" Air Bleeder Plug with Thin threads that can be found on the New style of a StaRite Dura-Jet DJ Series, Dyna-Glas/Dynamax, ABG, Dyna-Jet, TPE, Some StaRite Pool Multiports, Petair/...