Mr. Tuffy Tire Liner. Nothing ruins the Zen pleasure of a bike ride quite like getting a flat. That's where Mr. Tuffy tire liners come in as the perfect means to ward off irksome punctures. Made of durable, lightweight, and biodegradable polyurethane, Mr. Tuffy tire liners provide a protective barrier between your inner tube and road hazards such as glass, nails, thorns, and other sharp objects. Color coded by tire size, Mr. Tuffy will have you covered no matter if you're riding a BMX, road, cyclocross, or mountain bike. For additional size options see item MT SL2.