Machined aluminum shell slips together for precise bearing alignment and frame fit, reducing bottom bracket creaking and premature bearing wear. FEATURES : Replaceable Enduro bearings Made in the USA ABEC-3 sealed bearings Grade 10 chromium steel balls, 52100 High Carbon Chromium Alloy Races Each bottom bracket includes (2) silicone dust seals, (2) 0.5mm crank spindle spacers, and (2) 1.0mm crank spindle spacers