I had 3 flats in 2 weeks recently and was so frustrated. One was because of a piece of glass the size of a grain of kosher salt. Sliced right through my tire and into the tube. The girl at the bike store told me that some people would be thrilled to have only 3 flats on one ride. I actually carry 3 tubes with me now but I figure if I get 2 on one ride again then I'm heading home. lol