The Yankee Hill Machine HD 3-Lug Adapter is a quick-attach mounting option designed to provide added strength and longevity to your 3-Lug equipped firearm. This fully enclosed assembly contains a mounting interface machined from 17-4 Stainless Steel-making it durable and capable of handling heavy use-including full auto. The HD 3-Lug Adapter is HUB compatible and uses the iconic, HK tri-lug interface. This makes for a versatile adapter, capable replacing any 1-3/8"-24 mount. The HD 3-Lug adapter can be swapped onto your R9 or Nitro N20 Sound Suppressors, and can be used on some rifle calibers. This is the perfect upgrade if you are looking for a quick-attach mount with better longevity-especially on full auto platforms.FeaturesReplaces any 1-3/8"-24 MountAluminum and Stainless Steel ConstructionMatte Black Finish