This is a Gemtech Muzzle Brake known as the QUICKMOUNT chambered in 556NATO, model 12152.
The new GEMTECH Muzzle Brake is for users who want less felt recoil" less muzzle climb" and faster follow up shots. All 5.56mm QUICKMOUNTS fit the M4-96D" G5" G5-T" SHIELD" HVT-QM" QUICKSAND and ONE suppressors.
Features:
Blank Firing Adapter groove
Quickmount lugs for use with all Gemtech 5.56MM and .30 cal suppressors
Precision mounting shim kit