Wolf Tooth MK0 BSA Bottom Bracket - For 30mm Signed, Sealed, Delivered Ceramic bottom brackets have a reputation problem: fast out of the box, dead after a season of wet rides. The MK0 BSA's sealing system is engineered specifically to keep water, mud, and debris out by pairing silicon nitride ceramic bearings for the long haul. Custom polymer spindle bushings sit between the bearing inner race and the crank spindle, eliminating metal-on-metal contact at the source of most BB creaks. The cups spend extra time in the CNC lathe for aggressive material removal, so you get a lighter package without sacrificing strength. If you run a 30mm spindle crankset and a BSA shell, this is the thoughtful upgrade over a generic ceramic swap. Silicon nitride ceramic bearings with low-drag seals: harder and lighter than steel, with custom race sealing that keeps the bearings spinning fast in wet and muddy conditions Custom polymer spindle bushings: separate the bearing inner race from the crank spindle to cut out metal-on-metal contact, eliminating the creak at its root cause Adjustable-width sleeve fits 68mm to 73mm BSA shells: one BB covers both shell widths, with 83mm DH and 100mm fat bike sleeves available separately Standard 46-12 spline tool installation: installs and removes with tools you likely already own, no proprietary drivers required Designed, machined, and assembled in Minnesota, USA: fully rebuildable with replacement bearings, bushings, and o-rings available from Wolf Tooth directly SPECIFICATIONSWeight77g (includes complete BB assembly without spacers)Cups Material6061-T6 Aluminum Shell Material POMSeals NBR, Urethane Spindle Bushings POMBearing Ball Silicon Nitride Bearing Race AISI 52100 chrome bearing steel, hardened to Rc 60-65, with ACOSUR-ZNA corrosion resistant coating Included Spindle Spacers2x 0. 5mm, 2x 1mm, 2mm, 3mm, 5mm Included Shell Spacers2x 2. 5mm BB Shell Widths68, 73, 83, and 100mm BSA bottom bracket shells Included Internal Sleeve Adjustable-width sleeve fits 68-73mm BSA shells Add-On Sleeves Available83mm and 100mm width internal sleeves (sold separately) | Wolf Tooth Components | Mk0 Bsa Bottom Bracket - For 30Mm | Shadow Gray | 30Mm