A small adapter that allows mounting Picattiny-style gear (e.g. a tactical flashlight) on a helmet with OpsCore ARC rails.

Requires an 8mm M4 screw and an M4 nut - these are used to tighten the adapter in place and ensure it doesn't slip forward / backwards. Just insert the nut into the hole, and screw in the M4 screw. Once the adapter is in place on the helmet rail, tighten the screw to hold it in place. 

Print in PETG, or anything that is durable and has a little bit of flex. 

You should be able to print this with no supports.