Mounting rings are used for mounting the pickup and allowing height adjustment up or down for the desired pickup position. Mounting rings can be angled to fit the desired area from the neck to bridge position. With mounting rings, the pickup can be adjusted lower on one side and higher on the other. Usually the bass side is lower as the bottom strings can be fatter and louder sounding. Mounting rings are used to cover the routed cavity and to give an instrument a clean look. The majority of mounting rings have been injection molded out of black and cream plastics. Mounting rings used on Gibson Firebirds are stamped out of metal and plated either gold or nickel to enhance the appearance.