SnapCap Magnetic Valve Stem Covers are designed to replace traditional screw-on dust caps. A steel ring screws onto the existing valve stem threads, and the magnetic cap simply sticks to it. With 'hold-power' up to 1,000 times stronger than similar-size conventional magnets, the Magnetic Valve Stem Covers stayed in place in test speeds over 200 mph. They make valve access easier and, once removed, will stick to the fender or other steel parts, eliminating the chance of their getting lost while adding air.