MaxBlast Twin Mini Compact Horn is constructed of an injection molded housing under a stamped 304 stainless steel cover. Corrosion resistant stainless steel cover protects the the internal components. After a 600 hour salt spray test, this electric horn was completely rust-free! Mounting bracket can be used as a wiring template. When installed, horns should point slightly downward to permit water drainage. At 111 decibels and a frequency (Hz) of 490±20A, this horn meets US Coast Guard’s COLREGS and ABYC standard A-23 for use on vessels under 12m (39′). Five-year rust-free warranty. NMMA Type Accepted #2577062. 12 VDC.