This depends on a number of factors, service chosen, size of car, colour of paint and condition of the vehicle. It may not be obvious but if you have dark paint e.g. black and want it detailed you should chose a two stage machine correction, however if it is light coloured paint e.g. silver a single stage correction would be fine. This is because the marring instilled from the compounding stage where we are correcting the swirls and scratches will not be visible on light coloured paint.