Upgrade your XRS Cross Bars with additional 4-CORE Side Rails that connect the uprights on both sides of your truck bed. The Side Rail Accessory Kit provides additional mounting tracks for a variety of gear and accessories. The optional rail kits are installed using pre-drilled holes integrated into the corner uprights and supplied hardware. Available in 37 3/4-inch and 49 3/4-inch sizes, can be cut to desired length. The 4-CORE system is an extruded aluminum track system that works with any 1/4x20 hex bolt and is finished with a textured black powder coating. Works with both mid-size and full-size XRS Cross Bars (5935000T/5935001T). 5 year limited warranty.