For use on an adult tricycle with old fashioned plastic spokes that are too close to the valve stem and the tube has a short stem. It is not possible to grab the valve if the tire is too low. I would like to leave them on as you often have to inflate the tires. I will test for leaks. The valve extension has a threaded end for the cap. My noisy electric inflator has a good hose end that can grab a short tube valve and get past tight spokes, but my new hand pump has a heavier end that needs an extension valve. They don't do things as well as they used to, as I often say. ---UPDATE--- 1 star removed. Sometimes it takes a bit of fiddling to get smooth airflow between the extension and the bike's valve stem. The expansion is close to great so should be 4 1/2 stars. The problem is most likely how I use the extension, and the extension probably works well with a car tire or other bike tires. In fact, you won't find a better extension anywhere. UPDATE 6/27/2014 - I kept an extension on each wheel of the tricycle but found a couple of caps sticking out on the air intakes which required WD-40 cleaning so don't leave them on the wheels now. Note / I decided to add 1 star because the extension is really useful and well made. The problem seems to be in the pump valves and their connection.