Hot Wheels Track Builder System Power Booster Kit Hot Wheels Track Builder Systems stunt sets expand the world of play! Test the limits of your Hot Wheels vehicles with the super boosted performance of the Track Builder System Power Booster Kit! Add insane speed with power boosters when competing with friends! Build up to 4 different races with this versatile set! The Power Booster Kit includes 35+ pieces including 2 speed loops and two boosters so you can boost your crash, your loops and head-to-head races! The possibilities are endless with open system play!