Outside diameter: 1/2"/12.7mm Inside diameter: 5/16"/8.1mm (fits 5/16" or M8 bolts) Length: Varies-Choose Length Shape: Round Material Type: T-6061 Aluminum with tumbled aluminum finish Material: All of our unthreaded aluminum spacers and standoffs are made from quality aluminum alloy, which provides excellent strength, durability, and corrosion resistance. Heat Dissipation: Aluminum Spacers/bushings have good thermal conductivity, allowing it to efficiently dissipate heat from electronic components. Metal Spacers Online provides a number of aluminum spacer sizes and materials for home improvement, DIY, automotive, industrial and manufacturing applications. You are sure to find the metal spacer that you need from our Amazon Store. Many Available Sizes: Our aluminum spacers come in various diameters and lengths to accommodate different application requirements, please select the correct option from the menu that will meet your requirements. Other Metal Spacer Options: This aluminum spacer may also be available with a black anodized finish or in high quality mild steel material, please check our Amazon Store for other options. Round Aluminum Spacer