On the setup station deal.How many pros have you seen using one.To be honest most Ive seen setting up there cars use a shock oil bottle or something of that nature.As long as what ever your using is consistant it doesn't really matter.I've used rpm camber and toe guages for 10+ years and never had an issue.The most important thing is to know when you need more or less camber or toe and how it affects the handling of the car.