[Lightweight and durable] Qualified aluminum alloy material, solid and durable, and is made with fine workmanship, lightweight and durable[Waterproof and dustproof] Separate rubber seal, internal spring, to prevent water and dust, super waterproof and extend the service life[Ease of installation and operation] Smooth rotation, ease of installation and operation, which makes pedaling more labor-saving-Provides greater transmission of force from the pedal[Smooth rotation and wide application] Smooth rotation, easy installation and operation. Applicable for Shimano supplementary crankset, pinwheel, FSA supplementary crankset, Sunrace and SRAM hollow crankset etc. If only the diameter of the cylinder in the hollow chock is about 29 mmSuitable for bicycle frame five-way 68-73mm, threaded-1.37 x 24TColour: BlackMaterial: aluminum alloyPackage Contents:1 x bicycle bottom bracket1 x washerOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.