Took a while to break in, but after about 10 uses works everytime! The first couple uses it would not stay on the valve.
It should have been noted that this chuck won't work with Vittoria removable valve tubes. So for my clincher disc wheel with latex or butyl tubes it is useless. I will be taking it back.
James, the chuck when new can be rather tight and if it isn't sealing, it is because is is not pushed on far enough. It helps to put a little water or a drop of chain lube on the gasket for the first few uses to help it go on all the way, but once it is seated it will seal on any type or brand of valve stem. Thanks
Fits perfect to my silca ultimate pump
It really fits the space in any disc wheel, and stays on when pumping the tire to 170psi.