Hollow-forged aluminum arms with integrated spider Designed for 121mm (68/73mm shell) BB-spindle length and a 50mm chainline, use ES51/ES25 Octalink (OL9) bottom brackets *(sold separately) Includes 4-bolt 22/32/44t 9-speed SG-X Hyperdrive chainrings (black, aluminum outer ring with silver, steel middle/inner rings) 715g with rings @ 175mm