Feather Friendly Window-Strike Prevention Decals - 3 RollsStaff Favorite! This window decal system is scientifically proven to be the most effective form of after market window strike prevention! Creating a 2 inch grid of small dots on the outside of your window prevents birds from mistaking the reflection for a continuation of outdoor space, and for the human eye is still small enough to disappear from view! This pack includes 3 rolls of decal tape. Each roll treats a surface area up to 30 inches x 80