The difference as described by parents is that from a Volkswagen to a Mercedes. Every Skitter or Plasma Car comes standard with Black hard plastic wheels. The wheels are loud, slide on some surfaces and mark indoor floors. The upgraded wheels are made of polyurethane rubber and are special cut with a flat surface for better traction. The upgraded wheels provide a smooth, comfortable ride allowing for better performance and over all enjoyment for the child. ***The upgraded wheels will not mark floors.