Meets or exceeds U.S.C.G. and International Rules of Safety. Their distinctive sound is scientifically developed for volume, audibility and richness of tone on the basis of musical instrument design and economy of air consumption. Horn projectors come in your choice of cast bronze or spun brass. There are not moving parts other than the sound producing diaphragm. All horn castings are of bronze, accurately machined and neatly finished in plain brass, white powder coat, or chrome plate. The flange base is 3" in diameter.