The 9mm 3 Lug Adapter features Rugged Suppressors' 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 our Obsidian9 3 Lug Mount. This 3 Lug Adapter is made to 9mm HK spec. and is not compatible with 45ACP.*Rugged Suppressors recommends using Red Loctite and 20-25 ft-lbs to torque the 3 Lug Adapters onto your barrel.