Griffin Armament A2 Blast Shield/Optimus A2 Mount Muzzle Device Black. Compatible with the Minimalist brake shield thread protector and also capable of converting the Optimus silencer to an 8.4in OAL 17.4 ounce A2 mounted configuration. The device and the collar are both compatible with the car stock wrench tool included with the Optimus silencer. Additionally a strap wrench (not included) may provide useful utility especially when removing accessory mount interfaces from the Optimus silencer. Weighing 5.7 ounces the Optimus A2 mount can be used on 5.56mm AR's to and with the 30SD flash comp it will support centerfire calibers up to .308 Winchester. Minimum barrel length caliber ratings A2 mounted Optimus silencer with taper lok baffle: .308 on barrels down to 16in. 12.5in 6.8SPC 8in 7.62x39 8in 300BLK super or subsonic 10.5in 5.56mm Compatible Griffin Mounts: M4SD Tactical Comp M4SD Flash Comp M4SD Paladin Brake M4SD Hammer Comp 30SD Flash Comp A2 compensator Mounting Instructions The rear slip-coupler unscrews completely from the main body of the Blast shield. The coupler is slipped over the muzzle device at a 45 degree angle then straightened (with the threads away from the barrel) to allow the coupler to slip into the rear accessory/BFA ring of an A2 device. The tapered end of the main body of the Blast Shield is then inserted between the coupler and the muzzle device. The coupler is then re-threaded onto the main body of the Blast Shield while still in the accessory ring. Compatible Griffin Mounts: M4SD Tactical Comp M4SD Flash Comp M4SD Paladin Brake M4SD Hammer Comp 30SD Flash Comp A2 compensator. Mounting Instructions The rear slip-coupler unscrews completely from the main body of the Blast shield. The coupler is slipped over the muzzle device at a 45 degree angle then straightened (with the threads away from the barrel) to allow the coupler to slip into the rear accessory/BFA ring of an A2 device. The tapered end of the main body of the Blast Shield is then inserted between the coupler and the muzzle device. The coupler is then re-threaded onto the main body of the Blast Shield while still in the accessory ring. Specifications for Griffin Armament A2 Blast Shield/Optimus A2 Mount Muzzle Devices: Manufacturer: Griffin Armament Condition: New Color: Black Features of Griffin Armament A2 Blast Shield/Optimus A2 Mount Muzzle Devices: Minimum barrel length caliber ratings (A2 mounted Optimus silencer with taper lok baffle): .308 on barrels down to 16in. 12.5in 6.8SPC 8in 7.62x39 8in 300BLK super or subsonic 10.5in 5.56mm Package Contents: Griffin Armament A2 Blast Shield/Optimus A2 Mount Muzzle Devices Griffin Armament GAOPTA2: A2 Blast Shield/Optimus A2 Mount Muzzle Device Black