Shimano SM-BB72-41B is a press fit bottom bracket.
Small ball bearings help save on weight.
This Hollowtech II bottom bracket also has a shaft diameter of 24 mm, which has proven to be optimal in terms of stiffness and rotational efficiency.

Specifications:

• Application: Road, City
• Type: Press Fit BB86
• Shell Diameter: 41 mm
• Shell Width: 86.5 mm
• Axle Diameter: 24 mm (Hollowtech II)
• Bearings: Steel
• Bottom Bracket Cup Material: synthetic resin
• Small ball bearings for low weight