Made of solid CNC Billet Aluminum these handy Diamond Donut adapters makes it quick and easy to install a set of side rails into a toolbox. Just drill a carefully measured hole in the toolbox, mount the adapter with gasket on the toolbox and attach your side rail. Sold in pairs. Available in Chrome or Black. All installation hardware and instructions included. Sizes available to accommodate 1.75in., 1.9in. and 2.0in. diameter rails.