SC-1 bottom brackets are the perfect choice for those who still prefer the low weight and simplicity of square taper cranks. Each bottom bracket is hand assembled using a hollow chromoly spindle, precision sealed bearings, forged and CNC-machined alloy cups and a composite center spacer/seal. Hollow chromoly spindle CNC-machined alloy cups JIS square taper It offers exceptional durability and smooth operation. Plus, it's designed to provide efficient power transfer from cranks to chainrings.