Yes, the JAKL upper fits a standard lower. However, I'm not sure if you need their proprietary back piece, but they'll be a big hole/opening there w/o it.
Lower Build Kit: In this kit, you will find everything you need to convert your AR-15 Mil-Spec lower into a PSA JAKL Pistol Lower. Featuring a MOE A2 grip and PSA Triangle Side Folding Brace, as well as our enhanced polished trigger (EPT) which helps reduce pull weight, and is built to last. Also included are the JAKL stock adapter assembly & JAKL proprietary bolt catch that are required for your lower to function with our PSA JAKL upper assemblies.
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Comes with proprietary JAKL bolt catch that must be installed on the lower for proper function. Must be used with JAKL buffer system found on PSA JAKL lower or lowers built with a PSA JAKL lower build kit.
Ah ok. That answers my question. Thank you very much. Never thought of that upper piece.
As much as this is neat havin a folding option I’m honestly not bothered by and like the solidness of buffer tubes. May grow one on a 1913 pic adapter anyway.