XT SM-RT78 rotors are both high performance and lightweight, using the proven Shimano Centre-Lock system giving increased strength and security with an easy set-upPrecision cut and drilled heat treated stainless steel braking surface improves pad clearing in muddy conditions while aiding cooling under high loadLarge 5-arm alloy spider is a highly rigid and lightweight support for the rotor surfaceSuper polished braking surface gives excellent brakingperformance