The Rugged 3 Lug Adapter features our 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.