describeDimensions: Inner diameter of bearing: 21 mm / x Inner diameter: 6 mm / x Wheel diameter: 50 mm / x Thickness: 18 mm / x Shaft length: 36 mm.Installation: This simple luggage roller can be installed yourself without professional assistance; it's very convenient. Pay attention to tightening the wheels during installation to ensure smooth rolling of your luggage.Advantages: High-quality, solid, quiet, load-bearing variable-speed wheels with double bearings and flexible rotation.Carrier: a single suitcase can support a maximum load of 51 kg, without deviation, safe and reliable to use.Cleaning: The luggage spare wheel is easy to clean and the wheel can be removed for cleaning.Buyers must measure the following data for the luggage wheel,See what sizes it can scroll through:1. Measure the original outside diameter of the wheel (wheel size).2. Measure the width of the inner groove of the wheel (the width is the total installation width).3. Measure the length of the screw (without the nuts at both ends).4. Measure the width of the inner bore of the bearing according to the diameter and thickness of the pipe.Packing list: 4 replacement wheels (luggage and other products are not included)Notice:1) Due to manual measurement, there may be an error of 1 to 2 mm.2) Due to differences in monitors, the photo may not reflect the actual color of the item. Therefore, the color may differ slightly from the actual color. Please refer to the actual product.