These zinc anodes are cheap insurance that will reduce or eliminate corrosion of underwater equipment. Simply attach this 3/4 lb zinc anode to a submerged metal part of the equipment and electrolysis will corrode the zinc first. Each unit has 2 wires molded in to make attachment easy. Anodes should be changed when they have reduced to 1/4 their original size. 1" x 5". Useful in both fresh and salt water and wet earth.