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
Primary Airsoft HI CAPA HPA / M4 Adapter for WE Tech Magazine - Airsoft Extreme
Poseidon HPA Series Stormbreaka GBB M4 Adapter for G Model / Hi-Capa GBBP ( HPA Only )
STL file Hi-Capa HPA Angle M4 Adapter・Design to download and 3D print・Cults