The Shimano BB-UN300 is a sealed-cartridge square-taper (JIS) bottom bracket — a dependable, maintenance-free choice for commuter, touring, vintage and entry-level bikes. Dependable sealed square-taper bottom bracket — genuine Shimano, brand new. Will it fit? BSA English-threaded, 68mm shell, 113mm spindle, JIS square-taper. For square-taper cranks on BSA 1.37×24 frames. Not for HOLLOWTECH II / 24mm spindle cranks. Key Specifications Brand Shimano Series UN300 Model BB-UN300 MPN BB-UN300 Type Bottom Bracket Interface Square Taper (JIS) Thread BSA (1.37×24) Shell 68mm Spindle 113mm Bearings Sealed Cartridge Weight 280 g (9.9 oz) Color Silver Country of Origin Japan Condition Brand new — original Shimano packaging Technology Highlights ✓ Sealed cartridge for maintenance-free service. ✓ JIS square taper compatibility. ✓ BSA 68×113mm standard fit. ✓ Durable steel construction. What's in the Box 1 × Shimano BB-UN300 bottom bracket (68×113mm) Original Shimano packaging Brand new in retail packaging. Ships from Ontario, California (US domestic) · Estimated delivery 3–5 business days · Free 30-day returns.
