To keep weight down, tire manufacturers are using thinner rubber to make Fat Tires. This, plus the low recommended inflation pressure of 5-15 lbs makes them more susceptible to flats from road hazards, including thorns, glass, nails, and even rocks. Mr. Tuffy XL Series provides serious flat prevention for Fat Tire users. When placed between tire and tube, it provides a protective layer between road hazards and the inner tube. Thorns or glass that may penetrate the tire are blocked from the inner tube. Proven Tough - For over three decades Mr. Tuffy has been the world's leading flat-tire preventive with Millions upon Millions of satisfied cyclists. Easy Installation - No gooey mess. Absolutely, Positively will not cause tire or tube damage or loosen spokes