The JBU Aluminum piston is much stronger than stock pistons and is designed for heavily upgraded guns. This piston is especially well designed because the teeth section can be removed and replaced in the occurrence of a stripped tooth instead of replacing the entire piston. Also, the second to last tooth has been eliminated, a well known stress relief technique among master technicians. Aluminum pistons are much stronger than polycarb pistons but they also don't have as much forgiveness. To go along with a good aluminum piston you should also have a good set of gears, and they must be shimmed very well to avoid premature and uneven wear, and to avoid excess gearbox noise. Since Aluminum is heavier than polycarb it is highly recommended to upgrade stock gearbox shells to reinforced ones.
The use of aftermarket airsoft parts is not an exact science. Some parts may require fitting even thought they were designed to fit without modification. Professional installation of upgrade parts is highly recommended.