Tight enough tread spacing for high speed, drag-free onslaughts yet blocky and tall enough to really dig in when it comes time to slam on the brakes. Tough – A double layer of light casing, TCS Tough tires are composed of two full layers of casing, bead-to-bead, leaving no area unprotected on our burliest tires. FR – Fast Rolling, with WTB`s Dual DNA rubber compound that optimizes efficiency, traction and durability, A firm, long-wearing centerline tread with softer side knobs. TCS – WTB`s Tubeless Compatible System, sealant based tubeless system with improved bead shape. TT – WTB`s new triple compound, TriTec featuring a hard base level, medium center knobs and softer shoulder knobs for improved traction and performance. EBIKE25 – has achieved a passing rating for use with E-Bikes up to 25kph.