RAPID THREAD MOUNT 5.56 SP-RTMBFB-556 Manufacturer Model Number: SP-RTMBFB-556 Manufacturer: Wilson Combat Model: Whisper Muzzle Brake Type: Accessory-Parts Item Type: Accessory Finish: Black Melonite Shipping Weight: 0.3 Feature: For use with Whisper Silencers Feature: Includes Shim Set and O-Ring Optic Adjustable Objective: false Optic Reticle Illuminated: false