Yankee Hill Machine Co sRx Muzzle Brake, 1/2-28, Compatible with sRx Low Profile Adapter, Attaches to Suppressors with 1-3/8"x24 Thread Pitch, Black Oxide Finish YHM-4405-MB-28 Model: sRx Muzzle Brake Finish/Color: Black Oxide Fit: Yankee Hill SRX Manufacturer: Yankee Hill Machine Co Model: sRx Muzzle Brake Mfg Number: YHM-4405-MB-28