The Speedco Velox/M2 Youth Disc Brake Mounts are CNC machined out of 6061 aluminum. The Velox carbon and M2 alloy frames share the same disc mount for the youth sizes (Mini - Expert XXL) while the Pro Size frames have a different compatibility (M2 Pro or Velox Pro).
All of our disc mounts are compatible with a size 120mm disc rotor, and will not work with a 140mm disc rotor. For optimal braking performance, we always recommend a Shimano XT/XTR hydraulic braking system.