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
HPA M4 mag adapter for Hi-Capa US - OUTDOOR ZONE
STL file HI-CAPA to M4 HPA ADAPTER 🔫・Design to download and 3D print・Cults
STL file HiCapa to M4 - HPA Adapter 🔫・3D printing model to download・Cults
H-series m4 adapter Gen.3 - Creeper concepts
Pack HPA M4 mag adapter for Hi-Capa series
TAPP Airsoft Modular M4 Magazine Adapter for Gas Powered Airsoft Guns (Model: Tokyo Marui / WE-Tech Hi-Capa), Accessories & Parts, Airsoft Gun Magazines, Gas Gun Magazines, M4 / M16 - Evike.com Airsoft