Mavic Crossroc Roam 650b Tire - 650b (27.5") UST Tubeless Ready: Traction, control and lightweight The UST concept improves traction, control and comfort while reducing inertia and flats. Guard : the strongest tyre Dual ply construction makes for a super strong casing to prevent flats even at low pressure. ARC Compound: All Round Compound (60A) that makes a versatile and durable tire