This is a Midwest Industries Sling Mount known as the Sling Adapter, model MI-SBTSA.
SB Tactical Sling Adaptor made by Midwest Industries. Only works with the SB Tactical Braces: SBT" SBT5" SBT5K" SBTEVO.
Features:
MI patent pending design
Features an anti-rotation QD Socket
Allows the user to mount a sling to the side folding SB Tactical Arm Braces
