have a 11 yr old driver who will be 12 in dec. been looking into sprint racing . cadet or rookie karts are one size jr and adult another size. i do not want to get a kart for this year then get another next year. you need a different chassis for 4 cycle or 2 cycle motor rules and classes for the jrs are confusing . so many motors you can run. from what i can tell some of the rookie or cadet karts will be longer next year if you run a certain type of motor. you can run one body here but not somewhere else . it is confusing. if some one would help explain the differences it would help us decide to stay with dirt or go to sprint racing