Purchasing this pinion gear set, along with a set of spur gears for your chassis is a great way to improve acceleration or top speed of your RC car. I purchased every pinion gear from 19t to 25t for use in my TT-01, as well as the 55T and 58T spur gears. Using these gears has allowed me to perfect my gear ratio for my style of racing and the motor that I use.
I recommend you also purchase other pinion gear sets just like i did:
Tamiya (#50356) 20T, 21T AV Pinion Gear Set
Tamiya (#50357) 22T, 23T AV Pinion Gear Set