Airsoft Hi-Capa 5.1 Rail M4 Mag adapter V2 by Thor | Download free STL model | Printables.com
Hi capa HPA and M4 adapter for Tokyo Marui mags (L9B4K5UL5) by PrimaryAirsoft
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