MacCourt window well covers are designed to protect your basement from water, keep your wells free of debris and improve your basement's energy efficiency. They protect your basement by preventing water from entering through the window wells while keeping your wells free of animals, leaves and other debris. Made of clear plastic to let natural light into your basement they also improve your basement's insulation. This cover fits over window wells that are 40" or less in length and project 13" or less from the house. Inside dimensions are 41" W x 14" D x 11-1/4" H, while outside dimensions are 43" W x 14" D x 12" H.