-This pivot pin adapts Mil spec AR15 Uppers to an AR Lower with 5/16 front pivot pin hole diameter.
-Works with Colt SP-1 Lowers & other Preban AR15 lowers.
-Allows you to mount a variety of AR-15 uppers to a variety of pre ban lower receivers
https://www.thegunparlor.com/products/accessories-the-gun-parlor-702381354603-rs042-3873