You can find the LWRC Ultra-Brake 4 Port Muzzle Brake 5.56 here.

The LWRC Ultra-Brake muzzle brake has four large exhaust ports to vent gases to balance and mitigate recoil, which allows for faster and more accurate follow-up shots. This is the same great muzzle device featured on LWRC factory REPR MKII rifles. Includes a crush washer.

Color: Black
Caliber: 5.56/.224
Length: 2.25" Overall
Threads: 1/2X28