BIG PROBLEM WITH THESE. Based on the previous positive reviews I have to assume they are making them a bit smaller now to save $$. They are not big enough to fit on top of the Presta-Val (locking "button"). Assuming they were ok, I pushed on the presta valve - it was firm enough to pull the presta valve stem out with it when I removed it again. SCKS big time. cost me $8 for 20 minutes to replace the tube.