Comes with 12 sheets of semi-transparent, static-cling butterfly decals, each sheet containing 4 reflective decals, approximately 3.5 inches across. Choose from a variety of designs to perfectly complement your home décor. Save the beautiful birds you love. WindowAlert stickers act as a deterrent for wild birds from flying into glass windows and sliding doors. The specially designed reflective material in each window cling reflects ultraviolet sunlight as glowing warning sign for birds. To humans they appear as frosted or etched glass. Designed to be applied to exterior glass surfaces. Before application, ensure that your surface is thoroughly clean and free of any overlay, tinting, film, coating or other impurities. WindowAlert is the trusted source for prevention of bird window strikes and window collisions. WindowAlert first developed and pioneered ultraviolet window decals in Bend, Oregon in 2003. Decals are made in the USA. WindowAlert decals help prevent wild birds from accidentally striking windows. Each decal features a special coating designed to reflect ultraviolet sunlight. This ultraviolet light is invisible to humans, and to the human eye the decal appears as if it were frosted or etched glass. For birds - they see a brilliant glow, much like a stoplight - which deters them from colliding with your sliding door or window. WindowAlert decals come in several designs: Butterfly, Hummingbird, Fall Medley, Snowflake, Maple Leaf, Modern Squares, Classic Squares, Pinecone and Hawk. Product Specs: As a guide, the recommendation is one decal every 2" vertical and 4" horizontal area of glass. For best results, replace decals every 6 months or test with the WindowAlert UV Flashlight. What's in the box? You'll receive 4 sheets of leaf medley decals, with 5 decals on each sheet, for a total of 20 decals.