Drop-In Hidden Horn V.1 kit includes a horn plus one chrome and one white decorative billet snap-in grill. Hole size 1-7/8" x 3-3/8". At 106 decibels and a frequency (Hz) of 440±20A, this horn meets US Coast Guard's COLREGS and ABYC standard A-23 for use on vessels under 12m (39'). Constructed of powder coated steel and injection molded nylon. NMMA Type Accepted #2577064. 12VDC.