I have purchased three of these in the last two months. I only get a few rides out of them before I get a leak right at the valve stem. My local bikeshop installed the first time and after the first leak I went back to purchase another tube and showed them the problem. They said that I must not have had the correct tire pressure in them while I was riding. Everytime since then I have confirmed the tire pressure before the ride. These tires clearly have a design problem at the valve stem. They aren't worth the money.