Hop-Up Mechanism
The hop-up mechanism on a AEG is the instrument which supplies a back spin on the BB. The back spin enables the BB to follow a mostly horizontal or ballistic trajectory. In a AEG without a hop up mechanism or with the hop up turned off, the BB will have a very limited range, in most cases it will shoot out and arc quickly downward after approximately 20 feet. As the hop up is slowly adjusted, a rubber membrane called the hop up bucking is pushed downward by a small rubber nubbin. The extra pressure provided by the bucking puts a back spin on the BB and allows it to float in a straight path.

We'll be posting some pictures of the hopup unit here.