Russell and All,
Racer Sideways use 17″ rear wheels and 15″ or 16″ front wheels depending on the model. The wheel inserts from Racer Sideways wheels will fit in the equivalently sized Slot It wheels. The rear wheels on some models are 8mm wide and others are 10mm wide depending on the model. I am not going to be too hard on things like the inserts. As long as a car has inserts I will be happy with it.