For those looking for a bit of an upper hand in the field for their M4 or M16 metal gearbox AEG rifle, we"ve got the perfect solution. The all-new DBoys 500-round extended M4/M16 high capacity magazine comes from the factory with a 65% increase in BB capacity. Compatible with metal gearbox M4 and M16 AEGs from AGM, Classic Army, DBoys, Echo 1 and JG. OEM manufactured by JG, this metallic magazine features durable construction, and an excellent-quality finish.