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

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

$14.22
$14.22 $18.00
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Shimano BB-UN300 Square Spindle Bottom Brackets
  • Fits JIS square-taper cranksets
  • Crankarm fixing bolts sold separately
  • Hollow spindle
    Bottom Bracket Shell I.D. 1.37
    BB/Frame Interface English
    BB Shell Width (mm) 73
    Spindle Interface Type Square Taper JIS
    Spindle Length 123
    Defined Color Black
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    • A Promise of Reliability

      We guarantee your gear is ready for anything the road or trail throws at you

    • Expertly Tuned & Dialed In

      Every component is inspected and meticulously fine-tuned by our team

    • Rider-Verified Performance

      Gear that has proven itself on our own races, trails, and open road journeys

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    Passion drives us

    At SpokeX Bike Co., bikes aren't just our business — they’re our way of life. As a rider-owned and operated shop, every decision we make comes from firsthand experience on the trail, at the race, and on the open road. We know what it’s like to chase a new line, push through the pain cave, and celebrate the ride — because we live it every day.

    RIDERS WHO VALUE QUIET STRENGTH, TRUST SPOKEX

    • A Promise of Reliability

      We guarantee your gear is ready for anything the road or trail throws at you

      - Liam R.

    • Expertly Tuned & Dialed In

      Every component is inspected and meticulously fine-tuned by our team

      - Dan M.

    • Rider-Verified Performance

      Gear that has proven itself on our own races, trails, and open road journeys

      - Alex S.

    NEED HELP? FIND YOUR ANSWER HERE

    When will my order ship?

    Most in-stock items ship within 1–2 business days. Built-to-order products may require a little extra time.

    Do you offer fast shipping?

    Yes - we ship quickly across the U.S. and internationally. Delivery estimates appear at checkout.

    Is this product compatible with my bike?

    Check the specs on the page. If you’re unsure, contact us and we’ll confirm fitment before you buy.

    What is your return policy?

    Unused items can be returned within our standard return window. Custom-built products may...

    Is this product covered by warranty?

    Yes - all products include full manufacturer warranty, and we can help with any claims.