The BB30 bottom bracket allows you to pair 30mm spindle cranks to 42mm inner diameter bottom bracket shells. Cannondale pioneered this standard along with specially-designed cranks and many have found the benefits to them. Road versions have a 68mm width, MTB has 73mm. These are also the bearings you can use to replace bearings in PF30 cups.You have two bearing choices. The first choice is our low drag, long life Standard Bearing, with hardened-steel races and our super round CeramicSpeed balls. The second choice is our Coated Bearing, which uses those same balls installed on coated, hardened-steel races for longer life and less bearing drag.In The Box:- 2 bearings.- 2 1mm spacers- 2 0.5mm spacers.- 2 dust covers.- O-ring.- 10mm syringe of grease.- Sticker sheet.