I was unable to use the locknuts that came with the gauges and tighten them enough to read them. The valves were too short. It confused me at first because I thought the display wouldn't see them. The instructions say to try again! The choice is pretty easy once you figure out the menu. It's a little difficult to get an accurate psi reading, but they're probably closer than my other tire pressure gauges. This is a very wise decision. We'll see how it holds up.