This is an M-LOK helmet rail adapter for the MIRA TAPR ARC Rail Fieldlock Adapter. (MIRA TAPR ARC Adapter)
It allows you to slide the ARC rail connecter into this adapter for use with M-LOK helmets (like Hard Head Veterans helmets). I am still stress testing it to make sure it will not break unexpectedly during usage.
You can use COTS M-LOK nuts or print these, I have been using them and they work great so far MLOK T Nut (Thingiverse)
Story Time: So…. recently I purchased a TAPR to use with a Halloween costume and also just in case I need it. I also ordered the ARC fieldlock adapter and the M-LOK adapter to attach it to my helmet. Well… what had happened was that I received everything except the M-LOK adapter, they sent me a second set of just the ARC rail pieces.
I reached out, and after some back and forth they informed me that the M-LOK was out of stock and they refunded me and allowed me to keep the extra connectors. So, based on their pictures I designed this adapter to work in it's place, and save me 30 bucks.