AEG's Or Automatic Electric guns can run off a number of magazines dependant on the weapon system they are imitating. These magazines usually fall into three different categories - high capacity, Medium Capacity and Low Capacity (Or real cap). High capacity magazines are normally clockwork style with a reservoir that feeds a mechanism that pushes bbs up into the feeding chamber - this can include drum mags, Medium capacity magazines normally consist of a fixed spring system that pushes the bbs along a track and back into the RIF - these are normally loaded with a speedloader or a loading tool. Low capacity magazines are very similar to medium capacity magazines but with a lower BB count (Normally 5- BBs or less. Real capacity magazines are inline with the weapon system that your RIF is trying to imitate - For example a standard load on an M4 or AR15 would be a 30 round magazine so these airsoft mags would hold no more than 30 BBs on a spring-assisted track.