I've run Performance GT2/K on 6 different bikes with 4 different riders. I've put about 6,000 miles on my IRO with them & probably another 6000 to 9000 on the other 5 bikes. We have yet to flat. I spent about 10 minutes picking glass out of the rear tire on the IRO but none of the pieces had penetrated the belt. My fiancee ran over a nail about 3" long which became imbedded in the rear tire. She heard the noise so we stopped. I could barely pull it out without pliers, but no flat.