Wolf Tooth English (BSA) bottom brackets are engineered to be durable, reliable, lightweight, and smooth. The weather sealing is best-in-class, with o-ring seals on the spindle and inner shell, a wiper connection seal between the bearing and end cap, bearing race seals, and a labyrinth end cap design. To prevent creaking, spindle bushings separate the bearing inner race and crank spindle to eliminate metal-on-metal contact. The custom chrome bearings has been hardened for improved durability and reduced friction with ZNA corrosion-resistant coating, while the ball diameter, width, and counts were custom selected by Wolf Tooth for top quality based on spindle diameter. Wolf Tooth bottom brackets are machined at Wolf Tooth in Minnesota, USA.Best-in-class sealing protects bearings from water and trail debrisCustom polymer spindle bushings prevent creaking and prolong the life of the cranksetCustom AlSl 52100 chrome bearing steel hardened to Rc 61-66 reduces friction for smooth pedaling with ZNA corrosion-resistant coatingAdjustable-width shells allow English (BSA) models to fit 68 and 73 mm frame bottom brake shellsItem SpecificationsBB Shell Width (mm)68BB Shell Width (mm)73BB/Frame InterfaceEnglishBottom Bracket Shell I.D.1.37Defined ColorPurpleSpindle Interface TypeRaceFace EXISpindle Interface TypeShimano Hollowtech IIWeight83 Wolf Tooth English (BSA) Bottom Brackets Bottom Brackets UPC: 810159401289