Primary Airsoft Primary Airsoft Hi-Capa HPA M4 Adapter GEN4 for ALL Mags - BattleFlair BV
T-REX M4 adapter (adapter only) – Eurotactics
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