I bought these for my car but they are labeled for bikes... Works the same I think except the length is shorter than the car valve stem cap. The gasket looks well sealed and the quality is good so I'd say overall it's a good buy.
Pros
Suitable for cars and bikes: do you have a car valve on your bike instead of a French valve? Then hoods from WEIDEBACH are just right for you. Please check in advance which valve type is suitable for your bike.