The brand new, HEAVY DUTY 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.