THE VERY FIRST UPGRADE for anyone who has an FF03 chassis. Running a stock FF03 exhibits major body roll and these will help eliminate most of it. Has the usual Tamiya colour scheme for hardness: red for soft, yellow for medium, and blue for hard. Hard to mess up and easy to tune with. Again, if you're going to buy one upgrade for the chassis, this has to be it. Improves handling, lateral stability, and cornering predictability. A MUST HAVE.