valve stem extenders

I have the SS extenders from Napa, but which ever ones you buy make sure they are screwed on tight to the short valve stems. When I first put mine one I had a leak in the inner duel tire and could not see the tire was low. Once I found the leak and tighten the extender I have used them for 12 years with no further problems. Knowing what I know now I would check them with soapy water after they are installed including the valve stem itself. I had to replace one of those also.