This is the FIRST MUST upgrade for TT-01E. It's includes the bearings for the steering as well, which makes the car a lot better to control. If you have this upgrade you dont need to buy the "racing steering" upgrade, but only the small arms as regular update parts if you want to improve the handling even more (so you can adjust the steering). The metal bearings make the car runs smoother, the battery will hold longer. It also a MUST before you are upgrading the engine, gear ratio or other speed factors.. or you will either burn out your engine or damage your car with melting bearings, which will end up with burned out engine :)) As with many other items from rcmart, excellent quality for bugdet price!