[Diameter & note] - Bearing inner diameter 8 mm, gasket inner diameter 6 mm. Note: The spacer is suitable for 6 mm shafts, but if removed, the wheels fit 8 mm shafts. Shaft and screws not included. [Wheels] - These wheels are designed for luggage, training wheels, or children's indoor roller skating. Not recommended for use on uneven surfaces. [Sturdy material] - Made of high-quality PU material, wear-resistant and durable. Features 82A hardness for long-lasting performance. High-performance bearings provide stability and comfort. If the internal buckle in the wheel core is loose, add a small piece of paper between the white plastic lip and the bearing for better fixation. [Ultra-quiet design] - High-elastic material ensures smooth and quiet movement, ideal for indoor skating. Color: Black Material: PU Size: 64 x 24 mm Package Contents: 8 x Inline Skates Wheels Note: Light and display differences may cause slight color variation from the actual product. Measurement allowance: +/- 1-3 cm.