This wheel tyre is made from special wear-resisting non-slip rubber and aluminum alloy wheel hub, can to ensure the long-term use of length accuracy effectively) Feature: Wearproof, strong and durable Specification： Circumference：300MM Diameter：94mm Thickness：14mm Bore diameter：6MM Material：Hub aluminum，tyre: wearproof rubber For any technical support or suggestion, please kindly go to our forum.