Shimano BB-UN300 Bottom Bracket British Thread is A good quality bottom bracket for traditional chainsets Super-accurate bearings for smooth operation and improved durability Durable, hard-wearing sealed cartridge bottom bracket with square tapered spindle fitting.Maintenance-free sealed cartridge bearing assembly keeps out dirt, mud, and water for long bearing lifeFast and easy installation without adjustment Narrow body allows clearance for cable routing under the bottom bracketShimano BB-UN300 Bottom Bracket British Thread FeaturesMaintenance-free sealed cartridge bearingSquare tapered spindle fitting.