Powder coated steel and injection molded nylon. Includes horn plus one chrome and one white decorative billet snap-in grill. Hole size 1-7/8\" x 3-3/8\". Frequency of 370 Hz 20A, meets USCG COLREGS and ABYC standard A-23 for use on vessels under 12m (39\'). NMMA Type Accepted #2577065.