It is just a style of threaded insert. There are 2 types: one particular is built to sort a bulge over the back side on the panel for a screw is tightened in its threads. The other is similarly drawn in employing a screw, but is drawn into your sleeve https://ar15forwardassist22197.ampedpages.com/the-definitive-guide-to-rivet-nut-54262629