WindowAlert Maple Leaf UV Decal is designed to help prevent wild birds from accidentally flying into your windows. This innovative decal features a special coating that reflects ultraviolet sunlight, which is invisible to humans but appears as a bright glow to birds, similar to a stoplight signal. To use, simply apply the decal to the outside of your window. For results, place the decals starting at the center and working outward, spacing them at least every 2 feet across the glass. Scientific studies recommend positioning the decals 2 inches apart horizontally and 4 inches apart vertically for maximum bird protection. Model Number: