I have commuted over 15,000 miles on Specialize Turbo Aramadillos and only have had 2 flats, one from a faulty tube and the other because I let the tire wear down to far where cord was showing in some small parts of the tire and a piece of glass went thru the cord. But normally I crunch glass without fear of flats. These are the best tires on the market for flat protection. Are they heavy? yes, but you can counter some of that by using ultralight Specialize 65grm tubes or Mich 70gram tubes. Are they stiff? yes, because the sidewalls also have flat protection there as well-no other tire I know of does that. Great tire for commuting because you will have very little to worry about getting flats anymore.