Okay, those are plastic tire valve caps. They don't let water or dust into the tire nipples (this is important). Basic functionality "check". I'm writing this review to add a few discriminators that may not be obvious. First shipping is free - no need to buy $25 items (I'm too cheap to buy Prime). Second, these are the cheapest plastic caps I could find. And thirdly, they are slightly longer than my previous valve caps and cover the entire tire valve thread. I don't know how long it will take me to use 36 of these puppies but I would buy them again without a doubt.