The Strike Industries OPPRESSOR Universal 3-Lug QD Base Set gives you an additional mount for another compatible weapon so you can use just one SI OPPRESSOR Universal body and quickly swap between firearms. This 3-Lug quick detach (QD) base is a unique fitment only to the SI OPPRESSOR Universal and includes all the necessary hardware to install on a compatible individual barrel. Made from S45C steel and includes a 1/2 concentric shim washer along with a 1/2 and 5/8 crush washers. Purchase as a spare or replacement base or so you can save some money and reuse the same SI OPPRESSOR Universal body on multiple weapons.