We offer a 30 day, money back guaranty, so that gives you a chance to use them and figure out if they do what we say they do. It even states that there is a 30 day money back guaranty. Where is your local shop?Because if they didn't turn out to be what I thought they were, I wouldn't need them and that would would be a waste of $30. Please don't take it as a slam. I am very interested in trying them out. It would just be a lot easier if my local shop stocked them.