CRL's Plastic Lined Mirror Mounting Clips are designed to allow maximum air circulation behind the mirror and accommodate uneven wall surfaces. The Upper Clips are spring loaded to expand over the top edge of the mirror as it is being installed, and then return to a position where the mirror is held firmly against the wall. The Lower Clips support the weight of the mirror. A plastic liner inside each Clip protects and cushions the mirror. Four Clips per set.