This Aluminum spacer can be widely used in high-temperature, high-pressure, and highly corrosive pressure, valves, sealing parts of cylinder heads, and industries such as car, steel mills, chemical equipment, and engineering machinery.Specification Material: AluminumColor: SilverInside Diameter: 5/16" , 8.5mmLength: 2mmOutside Diameter: 20 mmCompatible Screw Size: 5/16" , M8 Screws BoltsSize: 8.5 x 20 x 2 mm / 0.335 x 0.787 x 0.079 inch (ID*OD*L)Packing List: 5x Round Spacer AluminumAdvantageMade of durable Aluminum material, which is hard, good performance, good electrical conductivity, corrosion resistance and can be used for a long time.Instruction Easy to use, just need to install on the screw bolts with proper diameter.NOTE: Please select the appropriate size according to your needs.