The BB30 bottom bracket allows you to attach 30mm spindle cranks to inner diameter 42mm bottom brackets.Cannondale pioneered this standard along with specially designed cranks and many have found the benefits for them.Road versions have a 68 mm wide, MTB is 73 mm These are also the bearings you can use to replace the bearings in PF30 cups.You have two heading options.The first option is our standard low strength and long lasting bearing, with hardened steel tracks and our super round CeramicSpeed balls.The second option is our Coated Bearing, which uses those same balls installed on hardened steel coated tracks for longer life and less rolling resistance.