Hi-Capa M4 HPA Adapter Lower by captaINstraiTJacket | Download free STL model | Printables.com
HPA Adapter to M4 Magazine for Hi-Capa Replicas - shop Gunfire
Primary Airsoft adapter installation tutorial HPA and M4 Glock + Hi capa - YouTube
I know a lot of people hate the Primary Airsoft adapters, but when it's 110° outside, a light kit is a life saver. Also a great first step into HPA : r/airsoft