Elite Force HK MP5 A4 Airsoft AEG Rifle - Elite w/ Avalon Gearbox. 243 Caliber Package Contents: Elite Force HK MP5 A4 Airsoft AEG Rifle What firearm models does the manufacturer say Elite Force HK MP5 A4 Airsoft AEG Rifle is compatible with? The manufacturer says that Elite Force HK MP5 A4 Airsoft AEG Rifle is compatible with Heckler & Koch MP5Elite Force 2262061: HK MP5 A4 Airsoft AEG Rifle - Elite w/ Avalon Gearbox