Airsoft HPA (US) New23-2 Male Quick Disconnect QD Push-In Fitting Assembly to 4mm / 6 - 6.35 mm OD Hose
https://www.vogueparade.com/shopping/EN/100005571/1/1005002723798056/airsoft-hpa-us-new23-2-male-quick-disconnect-qd-push-in-fitting-assembly-to-4mm-6-635-mm-od-hose//