Chemistry and head-to-head racing combine in this science racing set. Mix your own fuel, watch the reaction build in the clear fuel chamber - and get ready for your cars to blast off! Blast-off rocket cars indoors? Yes! With the parent-approved "No Mess Spill-Stoppers", mess is contained for easy clean-up in seconds. Customize your vehicles and test variability! Change the wheels, the weight, and even add a plow or ski.