This 3 Lug Mount replaces the piston assembly in your Obsidian45 allowing you to attach the 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 .45ACP 3 lug* or a .45ACP 3 lug adapter. - *This is compatible with B&T .45ACP integral 3 lug firearms.