Previously I used the aluminum models. Make sure you don't use them unless you're applying anti-seize or something that won't bind the valve to the cap. However, you must be aware that applying anti-seize to this section will get your fingers dirty. That is the solution. The presence of a plastic liner on the inside of the cap makes it prone to sticking. A simple but brilliant idea. I was just hoping they would have more color options, like a metallic color. I would buy another set in a heartbeat.