For protect birds no hit against the window. Effective - Made of Vinyl. These birds stickers with holographic reflection technology, can be produce a dazzling light under the sun rays reflection, doing a good job of keeping your furry flying friends from crashing into the picture windows! Easy install- Post to the outside of the window or glass. Peel it off, stick it on, done! Don't recommend to put it inside of the window/glass. Helps - Protect your feathered friends and prevents breakage. Occasion - It is a long-lasting self-adhesive backing that fit for smooth surface glass doors and windows. It will not a hesive residue on your windows.