The Masterlock Wall Mounted Key Lock Box features a wall mount design for permanent installation. Its large internal cavity prevents jamming, even when holding multiple keys. You can set your own combination for optimal security. A protective weather cover prevents freezing and jamming. The molded body and vinyl-coated shackle prevent scratching. The internal dimensions are 3-1/4in (83mm) H x 2-1/4in (57mm) W x 1in (25mm) D.