These magnets are perfect for outdoor activities such as magnetic fishing, treasure hunting, and retrieving metal objects in the water. They feature a countersunk hole and eyebolt for easy attachment. Each magnet has a pull force of 900 lbs, making them some of the most powerful magnets on the market. The diameter of each magnet is 3.54 inches, with a thickness of 0.98 inches. These magnets are made of neodymium, a rare earth element, which gives them their high strength and durability. With proper care, these magnets can last for many years.