This device is to be used with M4/M16 airsoft style AEG rifle magazines. The device fits over the fill door of the magazine, and acts as a funnel allowing you to more easily load BB's. It can also be used as a scoop to grab BB's from a bag, ammo can, box, etc..
What usually is a mess and takes forever (loading BB's into magazines) takes only seconds with this device. Saves loads of time between matches.