We bought a used car and the dealer put new tires on it. I suspect they replaced the TPMS valve stems which I strongly suspect were shorter than the original stems. They were short enough that I could barely remove the valve caps (without dropping them) and had a hard time gluing the gauge to the tires. Basically I had to remove the hubcaps/caps before I was done. It doesn't help that I have some arthritis. I was looking for short extensions but came across these and gave them an injection. I would appreciate that they added just over 1/2 inch, enough to clear the lid but not long enough to be vulnerable if my wife scratches the curb. Thread - but I re-read the description (and comments) and realized they are meant to ensure you no longer need the caps. I tried to get a close-up of the shop end so you can see that there is a relatively large "hatch". Very different from the typical Schrader valve with a small center pin and a relatively large cavity around it to collect all manner of road debris. I haven't had them that long, but so far they work great and I really like the design. ...I suppose if you're worried about dirt, a quick wipe of the tip might alleviate that problem. So far mine have stayed pretty clean even on our salty roads this time of year. Now I'm glad I don't have to mess with caps. and I have enough to put her on a second car.