Bb30 Mountain Bike Bottom Bracket Shells Are Wider Than Road, 73mm, And Share The Same Diameter, 42mm. The Bottom Bracket Here Allows You To Install Your Sram Or Quarq Mtb Crankset Into A Bb30 Mountain Bike.This Is How You Get Minimum Drag, No Adapters Necessary. Our Bearings Are Installed Into Aluminum Cups That Thread Together For Quiet Durability. The Cups Come With Ceramicspeed Bearings Installed, Coated Bearings And Hardened-Steel Races For Longer Life And Less Bearing Drag.In The Box: - Bottom Bracket With Bearings Installed.- 2 Dust Covers.- 2 1mm Spacer.- 2 0.5mm Spacer.- Ceramicspeed Longlife Grease.- Sticker Sheet.Technical Data: - Quarq And Sram Cranks Spin Better In Our Bottom Brackets. Ceramicspeed Coated Bearings Typically Have Frictional Drag Of 0.3-0.4 Watts Per Set. That Represents An Average 75% Drag Reduction Compared To Standard Bottom Brackets. The Hardened-Steel Races Feature The Ceramicspeed Balls That Are 100% Smoother And 15% Harder Than The Ceramic Competition. The Ceramicspeed Bearings Last At Least Three Times Longer Than Other Bearings.- The Coated Bearings Drop Friction Further And Increase Lifespan. The Coated Races See A 50% Drag Reduction And An Improvement In Bearing Life Of 60%.- 24mm/22mm Step-Down Thru-Axle Crank Spindles Are Compatible With This Bottom Bracket.- Performance Can Be Improved By Changing The Grease. Long Life Grease Comes Installed, But Can Be Changed For Lower Drag All Round Grease For Lower Drag Or Less Messy Conditions, And Race Day Grease For Less Drag And Cleaner Conditions Still. Maintenance Of Ceramicspeed Bottom Brackets:- We Recommend That You Follow Our Instructions On How To Maintain Your Ceramicspeed Bottom Brackets To Achieve The Lowest Friction And The Best Longevity.