Rotor made the BB30 24 Converter Mountain Bike Ceramic Bottom Bracket for people who want to run the crankset they like, regardless of spindle diameter. The BB30 24 makes installing a conventional 24mm spindle diameter in a BB30 frame possible. Buttery smooth ceramic bearings keep you rolling faster and longer inside of their aluminum cups. To add unrivaled protection against dust, water, and mud, ROTOR used new, non contact labyrinth seals. The plastic caps that snap into the bearings now provide some compressive relief in the slip fit between the spindle and the inside diameter of the bearings thanks to an updated design by Rotor.