1. One of the 4 I got didn't move enough (still mostly red on a properly inflated tire). It was either not calibrated properly or it was just stuck. Either way, terrible manufacturing/quality control.2. See photo (don't pay attention to the dirty rims!), they stick out too much! Look at your existing caps. Now imagine these over this cap - they stand out so much!3. The o-ring is either incorrectly selected or simply of poor quality. If the seal were flat and covered the entire base of the device, the air seal would be much more secure. In its current form, ill-fitting seals either get stuck in the tire valve or press unevenly and air escapes. I had to repeat the fit multiple times for each tire to get it right.