Features Wear-resistant,silent,load-bearing,double bearing,flexible rotation. Highly elastic,super quiet when rolling,shockproof,keeps the luggage contents neat and tidy. Specification Material:polyurethane( PU ),stainless Wheel Outer Diameter:45mm Wheel Wide:18mm Bearing Internal Diameter:6mm Axles Length:30mm,35mm Package Include 4 x Wheels 2 x Wrenches 4 x 30mm Axles 4 x 35mm Axles 8 x Washers 8 x Axles screws Pls kindly note that Before order,you will need: 1.Measuring the original outer diameter wheels (wheel size). 2.The inside of the measuring wheel groove width (width of the total installed width). 3.Through the length measuring wheel rivet screw screw (excluding nuts at both ends) 4.Measured through the wheel rivet screw diameter pipe thickness (ie bearing bore width) Note 1.The size of the set with the error of plus or minus 1 to 3 mm,can be adjusted using gasket,does not affect use. 2.Any question please kindly to contact us and we promise to work hard to help you to solve the problem. ^_^