The Brand NEW HEAVY DUTY 3-Lug Adapter is a quick-attach mounting 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 of replacing any 1 3/8-24" mount. The HD 3-Lug Adapter can be swapped onto your R9 Sound Suppressor and can be used not only for 9mm but for 300 BO Subsonic (Only) calibers rifles and PCC. This is the perfect upgrade if you are looking for a quick attach mount with better longevity especially on a FULL AUTO platform. Replaces any 1-3/8-24" Hub Compatible. Aluminum and 17-4 Stainless Steel Construction. Black Oxide.