Shimano BB-UN300 Bottom Bracket - English, 73 x 123mm Spindle, Square Taper JIS

The Shimano BB-UN300 bottom bracket is built for frames requiring a 73mm English-threaded shell paired with an extended 123mm spindle length. Engineered for reliable, everyday crank rotation, this cartridge unit utilizes a hollow spindle to balance weight and strength while providing a secure fit for JIS square-taper cranksets.

Finished in black, this brand-new assembly threads cleanly into standard 1.37-inch inner diameter bottom bracket shells. Crankarm fixing bolts are not included and must be purchased separately.

Key specifications:

• Frame interface: English threaded (1.37-inch I.D.)
• Shell width: 73mm
• Spindle length: 123mm
• Spindle interface: Square Taper JIS
• Spindle type: Hollow
• Color: Black