Box Two integrated headsets feature an aluminum top cap, CNC-machined bearing cover, and split crown race with super-smooth rolling, precision bearings. The 1.5″ headset is designed solely for tapered frames and forks but also includes an adapter which allows you to run a straight 1-1/8″ inch fork in a tapered head tube. It has a 45×45 upper bearing and a 36×45 lower bearing.