I bought these tire valve caps because every time we take our machines to change tires the workers put the valve caps back on the valves to keep them hanging loose. I try to remember to tighten the caps but sometimes I do and the next thing I know I'm missing a valve cap or two. I would go to my local auto parts store and buy a matching set (4) of valve caps a few times a year so I could replace them if they got lost. The matching sets (4) I bought are about $11 a set. Next time I came back for them there was something else in the store like metal skulls with red eyes and that's just not me. I wanted a good solid metal valve cover with a rubber washer inside to isolate any air leaks. I don't know why I watched Revane but I'm glad I did. I found this set, high quality metal, rubber gasket and hex shape for easier tightening. 12 for the price I paid for 4. Now I have a lot of high quality parts, all the same and they don't have skulls on them; (No offense if you like skulls). Highly recommended, great material, great price!