The Yakima End Caps are replacement parts for your pre existing rack system. Designed to fit on the ends of your Crossbars. The End Caps keep the rain and dirt out of your roundbar to help prolong the life. By blocking out the rain and the dirt the Crossbars are less likely to rust and this will aid in ensuring your Yakima product is with you for a long time to come. Remember end caps come with the Control Towers not the Crossbars so if you order new crossbars be sure to order a new set of End Caps.