6061 aluminum hub shell with 6-bolt disc brake mount 6al4v Titanium freehub body 11 speed (9/10 speed compatible when used with included spacer - except XD) High quality sealed bearings resist contamination Durable chromoly axles RR 11/12s XD 32H 12TA AL6061 Sil 306 6B 148mm 60 60 36.5 22.5