Aluminum body with die casting aluminum head, powder coated for extreme climatic conditions 16 TPI Aluminum thread for matched fitting of horns. New improved forging t-yoke and plate for exquisite sound and long durability. High Quality Y-30 Approved Ferrite Magnets Weather-proof and rugged body. High SPL, crisp penetrating sound. Degree of protection IP 66 provided, when mounted on a reflex horn, against foreign particles such as dust and jets of water thus making them ideal for outdoor use.