Primary concern is quality of plastic anchors and screws provided with mirror. Anchors are too light weight for such a large mirror (3' X 5'). Drilled 1/4" holes and inserted anchors per instructions. Screws were not large enough in diameter to make anchors expand inside sheetrock. I used more substantial anchors and screws that I had on hand. Manufacturer - please spend a few cents more to provide better fasteners with the mirror. 
A couple minor blemishes on mirror, but hardly noticeable.