Elite Force HK UMP 400rd Hi-Cap Magazine Black. Our 400-round HK UMP AEG magazines are made of high quality polymer so they don t weigh much yet hold up well under rough conditions. No one likes running short on ammo so be sure to pick up a few extras for your HK UMP AEG before you head out to the field. Specifications for Elite Force HK UMP 400rd Hi-Cap Magazine: Manufacturer: Elite Force Color: Black Fabric/Material: Metal Magazine Capacity: 400 Round Projectile Caliber: .243 Caliber Package Contents: Elite Force HK UMP 400rd Hi-Cap Magazine Elite Force 2275006: HK UMP 400rd Hi-Cap MagazineBlack