This Clutch-Lok QD mount doubles as a flash hider for Sigs 5.56MM SLH/SLX suppressors. It offers a quick and simple attachment of suppressors and reduced muzzle flash when the suppressor is removed. Shoulder Interface: 25-degree taper for use with SIG SAUER Taper-Lok barrels. Model Clutch-Lok QD Series Flash Hider Material Stainless Steel Thread Pattern 1/2"-28