Tuning-up your chassis One of the great things about an assembly kit is that you can add a whole range of option parts (sold separately) during assembly, allowing you to easily tune-up the hard to get at places. With these option parts you can not only improve performance, but you can make a truly unique machine suited to your driving experience and needs. *The above photo is an example of a chassis fitted with option parts. Click the links for more information. *Click here for a complete option parts guide.