As I recall it was very rare for wheels to be provided in 4mm kits due to the variety of gauges available - 16.5mm, 18.2mm and 18.83. If all 4mm kits were provided with 16.5mm gauge wheelsets someone from the 18.2mm or 18.83mm fraternity would invariably complain. Way back in my 4mm modelling days it was always wheels (and motor) extra.