Made entirely of the highest grade, genuine cow, calf and lamb leather, they’re available in a wide range of colors and finishes, all roughly one millimeter thick (allowing them to work with bumpers and other cases). The removable leather covers apply with a thin layer of adhesive that apparently leaves no residue if you decide to quit it. Protect your phone (well, from scratches) or just use it for a more stealth look. » Valentine: Premium Leather iPhone 4 Backs