... high concentricity 4.No bubbles 5.Smooth surface ModelPU Ring wheel with aluminum core BrandKamidMaterial Nature rubber, NBR ... 95ATemperatureup to 300°CHub MaterialAluminum, Steel, Sintered Bronze, Brass, Bearing, Many PlasticsBearing ChoicesBall, Needle, Sintered Bronze, ... dimension & qtyWarranty6 months ~ 12 months. PU Ring Wheel with aluminum core, high precision, no bubble