The Rugged Suppressors 9mm 3 Lug Adapter features the patented Go/No Go Gauge. The No Go/Go Gauge provides confirmation that your suppressor is properly attached, for a surprise-free shooting experience. This 3 Lug Adapter is compatible and used in conjunction with the Obsidian9 3 Lug Mount. Made to 9mm H& K specifications. NOT compatible with .45 ACP. Red Locktite & 20-25 ft-lbs to torque the 3 Lug Adapters onto your barrel. Available Thread Pitch Options:1/2x285/8x241/2x36M13.5x1 LH Rugged Suppressors Obsidian9 M13.5x1 LH 3-Lug Adapter OA004