Using not only rider feedback experience & knowledge weve taken tread design a step further by manipulating each knob of the Fast Trak with FE Analysis. The result is less rolling resistance more traction when you need it all in a lightweight package. Adaptive Tread technology for Competitive XC riders.> Casing: 420/D1 for 15% enhanced cut resistance> Bead: Foldable> Butyl wrapped bead = 2 Bliss Ready> Compound: 60a> 26&34; x 2.0; psi 35-65> 29&34; x 2.0; psi 35-65