Shimano SMRT64 rotors offer secure & easy set-up with the proven Centre-Lock mounting system Precision cut stainless steel braking surface improves pad clearing in muddy conditions while aiding cooling under high load Rotor contact surface has been developed for excellent pad clearing & cooling which increases pad performance & life Alloy spider supports rotor surface&44; increasing rigidity & reducing weight Comes complete with steel lockring Average weight for 160 mm rotor with lockring is 153 grams