The S-Works crankset is 165 grams lighter than Dura-Ace while providing 11% increased rigidity. These incredible riding attributes were achieved through Specialized's FACT (Functional Advanced Composite Technology) Carbon monocoque crankarms that are co-molded to the oversize hollow-aluminum bottom-bracket axle. The crankset requires an oversize bottom bracket on the frame, too, so you will only get this crankset on the Tarmac SL complete bike!