Staun are next to useless...sorry but we have had 2 sets and they are inaccurate to say the least, frequently resulting in tyre pressures going too low tyres and coming off the bead. So you need to check them regularly including when they are working - which is time consuming and sort of defeats the auto - purpose really.
The ARB valve removing unit is fast to operate and accurate too and you can read the pressure as you go thereby ensuring it is what you want every time - though I heard some of the early units had a problem with the sliding bit sealing properly.....hum

