Thick, triple-ply top and single-ply sides Thick, triple-ply top and single-ply sides against rain, snow and scratches for all-weather protection. Reduces premature aging of RV and helps maintain resale value. Air Vents Air vent system reduces wind stress and vent inside moisture Elasticized Hem Extra reinforced corners with elasticized hem for custom-like fit and prevent tearing of your cover Tension Panels Innovative cinching system with tension panels to remove slack How to measure your RV? Please measure your RV to ensure a proper fitting size.Overall length includes bumper ,but not hitch. Pls add 1 foot to total length if you have a roof mounted AC unit. Measurement including spare tire if mounted to the back of your camper.