This 3 Lug Mount replaces the piston assembly in your Obsidian9/45, allowing you to attach the Obsidian9 or Obsidian45 to 3 lug compatible firearms. This mount is designed to be internal so that your overall firearm length is as short as possible. Using a 3 Lug Mount allows you to quickly attach/detach your suppressor to fixed barrel firearms, without having to worry about suppressor walk-off. Note: This is the suppressor mount only. To attach, your firearm must have an integral 9mm 3 lug or a 9mm 3 Lug Adapter.