5MM Spur to pinion adaptor allow you to go with bigger gears for your pinion. This listing is for 1 spur adaptor. Fits 5mm motor shafts. Use a spur gear as a pinion gear. Will fit Traxxas 1/10 spur gears, the flat revo/ e revo, emaxx and the curved rustler spur gears. This will help you get that record breaking speed run. Start with smaller gears first and check your temps and make sure your brushless system can handle the power draw of gearing up big. I know there are people out there trying to get that E Revo to 100mph, I think this will help you. Make sure you have the space in you car to install a bigger gear. Spur gear adaptor and screws only. Does not come with any gears or motor. Also have 8mm and 6mm spur adaptors.