Molded-composite rear upright features built-in 0° of outboard toe to improve traction and prevent suspension geometry changes in serious crashes. Features two roll center positions on the top of the rear upright. Accommodates small but robust 5x10 ball-bearings for minimized unsprung weight.Medium rigidity (labeled M) specially optimized for rubber-tire racing.Use on both left and right sides of the car. Can be also used for foam tires.