If you need to upgrade or replace your gears or the entire gearbox we have options here for you. As you upgrade your airsoft gun to shooter faster, the spacing of the gear teeth, or gear ratio, will need to need to get tighter to keep up with the increased performance. Especially when upgrading guns to take batteries with voltages higher than 9.6v gear, upgrading the gear set will become important however things below that voltage your standard gear ratio will work. If you're unsure about changing out the gears yourself, why not pick up a complete gearbox that you can "drop in" or swap for your upgrading or repair needs.