Upgrade your drivetrain with the reliable and time-tested Shimano BB-UN300 Square Taper Bottom Bracket. Built with Shimano’s proven sealed cartridge design, the BB-UN300 delivers smooth pedaling performance, low maintenance, and long-term durability for city bikes, hybrids, commuters, touring bikes, and classic Dutch bicycles.

Ideal for replacing worn-out square taper bottom brackets on both modern and vintage-style bikes.

Features

• Durable sealed cartridge bearing system
• Traditional JIS square taper spindle
• Smooth and dependable operation
• Low-maintenance design
• Steel body construction for durability
• English/BSA threaded shell
• Compatible with many Shimano and square taper cranksets

Specifications

• Brand: Shimano
• Model: BB-UN300
• Interface: Square Taper (JIS)
• Threading: English / BSA
• Shell Width Options: 68mm, 73mm
• Spindle Lengths: Various sizes available
• Use: City, Hybrid, Touring, Dutch Bikes, E-Bikes, Vintage Restorations

Common Sizes Available

• 68 x 107mm
• 68 x 110mm
• 68 x 113mm
• 68 x 115mm
• 68 x 118mm
• 68 x 122.5mm
• 73 x 113mm
• 73 x 118mm
• 73 x 122.5mm

Compatibility Notes

Please confirm your:

• Bottom bracket shell width
• Spindle length
• Crankset compatibility

before ordering. If unsure, contact us and we’ll help determine the correct fitment for your bike.