Accu-Pressure Safety Tire Caps, Set of 4 (30 psi)

I had high hopes for these. Bought several sets, put them on all my three cars' tires. Then this spring when changing back to summer tires from winter tires I decided to do pressure checks on the remounted summer tires. All had Accu-Pressure caps on them and all the caps showed green. When checked with my tire pressure gage, all were 10 psi down from the nominal value stamped on the caps.

The caps are worthless junk, in my view. Car and Driver tested them a while back and found pretty much the same thing.