[Diameter & note]- Bearing inner diameter 8 mm, gasket inner diameter 6 mm. Note: The spacer is suitable for 6 mm shafts, but if you pull it out, the wheels are suitable for 8 mm shafts. The package does not include any shafts or screws. [ wheels] - These wheels are mainly used for luggage, training wheels or children's indoor roller skating. It is not recommended to use on uneven ground. [Sturdy material] - These rollers are made of high-quality material, wear- and sturdy. Designed with 82A hardness to provide a long-lasting experience. Its high-performance bearings stability and comfort. If the buckle inside the wheel core is loose, it is recommended to add a little paper between the white plastic lip and the bearing to better fix the wheel. [Ultra-quiet design] - High-tech elastic material makes movement easy and noiseless, allowing you to enjoy skating time. colour: Black Material: PU size: 64 x 24mm Package Contents: 40 x Inline Skates Wheels Only the above package content, other products are not included. Note: Light reflection 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.