Adapt your Colt large pin upper to fit your small pin lower with this offset adapter bushing.
On the Colt AR15/M16, the front pin that joins the upper receiver to the lower receiver is larger than the pin hole on the popular new standard AR15 lower receivers. This is the pin the barreled upper hinges on when disassembling the rifle. This offset adaptor bushing has a larger diameter center section that is also off center. This allows a modern small pin lower to fit onto a Colt large pin upper. The offset center bushing section allows positioning for the tightest fit.

Approximate Dimensions – O.D. .312″ |  I.D. .247″