[Diameter & note] - Bearing inner diameter 8 mm, gasket inner diameter 6 mm. Note: The sp is suitable for 7 mm shafts, but if removed, the wheels fit 8 mm shafts. The package does not include any shafts or screws. [Wheels] - These wheels are designed for luggage, training wheels, or children's indoor roller skating. Not recommended for use on uneven surfaces. [Sturdy material] - These rollers are made of high-quality material, wear-resistant and durable. Designed with 82A hardness to ensure long-lasting performance. High-performance bearings provide stability and comfort. If the internal retaining ring in the wheel core is loose, it is recommended to insert a small piece of paper between the white plastic washer and the bearing to secure the wheel. [Ultra-quiet design] - High-tech elastic material ensures smooth and silent movement, allowing for quiet operation. Color: Black Material: PU Size: 64 x 24 mm Package Contents: 8 x Inline Skates Wheels Only the items listed above are included; other products are not included. Note: Lighting and display differences may cause slight variations in color between the image and the actual item. Measurement error allowance is +/- 1-3 cm.