Hollowtech II is using 24 mm axle and bearings. Shimano made the decision to adopt the 24 mm diameter axle and bearings to provide the best balance of rotating performance / stiffness / strength / sealing / weight in Shimano Quality.
|SERIES||SORA R3000 Series|
|Threaded BB shell width_70mm||✔|
|HOLLOWTECH II BB_Threaded BB type||✔|
|Threaded BB shell width_68mm||✔|