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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.