These mirror bottom J-channels are constructed of extruded aluminum and come in a bright silver painted finish. These mirror supports can receive a maximum glass thickness of 1/4 inch(when padding is not used and channel is mounted with nails), and span a total of 6 feet in length. These mirror bottom J-channels are designed to resist rust and corrosion, and they can be cut down to any desired size. Mirror tracks like these are easy to install, and used by many.