Drop-In Hidden Horn V.3 with Grills Drop-In Hidden Horn V.3 with Grills is constructed of powder coated steel and injection molded nylon. Kit includes horn plus one chrome and one white decorative billet screw-in grill. Hole size 2-3/4" diameter. At 111 decibels and a frequency (Hz) of 370A 20A, this horn meets US Coast Guard's COLREGS and ABYC standard A-23 for use on vessels under 12m (39'). 12VDC. NMMA Type Accepted #2577066.WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer, birth defects or other reproductive harm. For more information go to P65Warnings.ca.gov.