Hollow-forged, 2-tone aluminum arms with a reinforced spider and an integrated, HollowTech-II (HT2) bottom-bracket spindle for improved power transfer 4-arm 64/104mm BCD with aluminum outer / composite-reinforced steel (32t only) middle / steel inner SG-X chainrings with pins/ramps for precise shifting Included wide-stance bottom bracket cupset with outboard bearings offers increased rigidity (BB92 and BB30 adapter bearings available separately) Designed for a 50.0mm chainline and 135mm hub/frame spacing 895g with rings and BB @ 175mm