First step, check your cranks to find the axle type you have. We support 24mm, GXP, DUB and 30mm which covers 99% of the market. Second step, choose the fitting your frame has, please dont ask as googling it for you is pretty inaccurate. We support most of the fitments on the market. Thirdly select your bearings, We offer SKF in standard bearing sizes, our high end ceramic bearings and also a high quality standard bearing fitment. All our bearings come with high greasefill of waterproof grease and seals which actually work. Dont believe the snake oil spinny crank videos, that just shows how poor the sealing and clearances are, quality bearings have low friction UNDER LOAD. All of our bottom brackets are rebuildable with new bearings for long life.