Cow magnets are rod magnets with rounded ends. They are usually about 3"long and 1/2" diameter. These are popular with dairy farmers and veterinarians to help prevent Hardware Disease in their cattle. While grazing, cows eat everything from grass and dirt to nails, staples and bits of bailing wire. Tramp iron tends to lodge in the honeycombed walls of the reticulum, threatening the surrounding vital organs and causing irritation and inflammation, known as Hardware Disease. The cow loses her appetite and decreases her milk output, or her ability to gain weight . Cow magnets help prevent this disease by attracting stray metal from the folds and crevices of the rumen and reticulum. One magnet works for the life of the cow!