If you ordered the MTX3 Prospec, the gearing out the box is right on and you should not have to change to much after that except to have a few extra's gears on hand
Sounds like you guys don't play around much with gearing or run on differing tracks frequently......My personal opinion is that having a wide selection of gearing is VERY important for any racing vehicle.....especially one where the tire-size changes like the foam tires we are racing on.....
It will work on ANY clutch gearing and on ANY cars that has the Centax clutch.
Clarification.....will work on Centax II clutches (HPI, MTX-2...etc).....will NOT work on Centax III's like the Serpent 710 (and maybe G4).