Usage Tips:Professional front/rear hub nuts for kids bikes, banlance bicycles, push bikes Made of aluminum alloy material, light weight, high strength and durable. Anodized, anti-slip surface and bright color, corrosion-resistant and fashion. This serves to distribute the pressure of the nut over the part being secured, reducing the chance of damage to the part and making it less likely to loosen as a result of an uneven fastening surface. Specification: MaterialAluminum Alloy Screw Height: Approx. 8mm/ 0.3 inch Screw Outer Diameter: Approx. 17mm / 0.66 inch Nut Outer Diameter:Approx. 12.9 mm/0.5 inch Nut Inner Diameter:Approx.8mm/0.3 inch Package Includes: 2 Pieces Kids Bicycle Hubs Nut Note: Please allow slightly difference due to manual measurement. Color may be slightly different since different monitor. Thanks!