I'm sure you searched the web for reviews on them. I did... I bought two of the recommened ones.. just to make sure they jive with each other.. I have a quality Dually gauge from Napa that is the bar type that pokes out when pressure is applied and read on the bar.. I found that it is off by 5lbs psi compared to the Accutire MS-4021B Digital Tire Pressure Gauge and other digital one like it I have.. so good luck.. short of spending $150 for a calibrated kind.