Injection molded polymer body is lightweight but can withstand the rigors of field use Easy to use winding mechanism ensures proper feeding 400 round capacity Metal magazine stem Easy to fill design Provides more firepower than standard extended magazines Huge gas reservoir Manufacturer: AW Custom Specifications: Capacity: 400 rounds Gas Type: Green Gas Compatibility: For WE Open Bolt GBB M4/M16 and other compatible gas rifles Material: Polymer, Aluminum Alloy