The Rotor BB1 Road Bottom Bracket may lack some of the weight savings and sheer sex appeal of Rotor's BB1 Zero Ceramic upgrade, but it still provides your Rotor 3D cranks with a silky smooth and infinitely serviceable interface; a culmination following years of intelligent engineering and careful pro-team testing. Over the course of their relationship with Cervelo, Rotor engineers have been lucky enough to have immediate pro rider and mechanic feedback in making improvements on a few small details of the oft-overlooked bottom bracket. The seals have been vastly improved, as external bearing bottom brackets of this type have long been known to possess a considerable greater amount of drag compared to some of the benchmark bearing assemblies from earlier generations (think Campagnolo Record square taper). Rotor also thought to improve the plastic caps that snap into the bearings. We often call them dust caps, but they have a structural place in the bottom bracket system, providing a bit of compressive relief in the slip fit between the spindle and the inside diameter of the bearings. But as they also provide a built-in washer between the crankarms and the inner bearing race, too much compression or deformation under load could result in poor bearing preload and lateral misalignment as you pedal. Rotor has eliminated any chance of this and the result is better shifting. The Rotor BB1 Road Bottom Bracket has Black anodized CNC machined 7075 alloy cups. They are threaded to fit 68mm English bottom bracket shells. This bottom bracket will fit all Rotor and Shimano compatible cranks with a 24mm spindle.