Ideal for KELVIN® Solar Racers™ and other projects.
This kit includes  front wheels with a rim (you can add a rubber O-ring tire on the rim but it is not included and not required). In addition,  back wheels with a rim and a built-in gear with a 2-gear ratio. The built-in gear fits a 2mm toy motor shaft and matches the big back wheels. Finally, the kit includes  axles (you can also use 1/8 in. dia. axles available for wheels). The axles are 2-1/4 in. long.