AFX introduced the SG+ in the 1980's which has become a very desireable chassis. The original issue came with 2 polymer tractions magnets which created exceptional handling capability. They have since changed over to ceramic magnets which do not hold quite as well. The chassis comes with adjustable timing so that you can fine tune your performance requirements. It also comes with a separate body clip which is used to allow for the mounting of the stocker and any other wide body AFX cars.