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 adapter M4 charger for Hi-Capa series
STL file Hi-Capa HPA Angle M4 Adapter・Design to download and 3D print・Cults
Primary Airsoft adapter installation tutorial HPA and M4 Glock + Hi capa - YouTube