700c models will also work with odler 27in tire sizes. StopFlats Tube Protection Tire Liner is the best protection against flats. STOP Flats2 is a remarkable tire liner made of durable, lightweight polyurethane. When inserted between the bike 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. Comes in many sizes to fit your tire. Features: Sold as a pair. Includes liner for front and rear. Hardened outer layer stops throns, broken glass, and trail debris. Ultra-soft inner layer cushions the inner tube. Weighs less than liquid fills. No gooey mess.