Box Two Hubs feature cold forged & CNC-machined, 6061-T6 aluminum shells fitted with precision sealed bearings & 20mm, 7075-aluminum axles & axle nuts. Besides 100mm long front & 110mm long rear spacing, they also feature oversize, 32mm dropout interface washers, which further increases the stiffness of the wheels. section Product Specs HUB TYPE: Cassette AXLE: 20mm DRIVER: Sold Separately SPOKE HOLES: 36h WEIGHT: 479g/16.9oz