PlateMate offers a unique micro-loading product in the form of weighted magnets that add small, incremental resistance to barbells, dumbbells and weight stacks for smaller weight jumps and safer workouts. The lighter PlateMate weights are especially useful for rehabilitation. The Donut magnetic attachment is specially designed with a hole in the middle that will clear the chrome washer and hex bolt found on pro-style dumbbells and barbells. PlateMate donuts are primarily used for pro-style dumbbells and fixed barbells with solid steel or painted cast iron plates, Power Block dumbbells and weight stack machines. PlateMate weights include super-strong, rare-earth magnets that stick to cast iron and steel dumbbells, barbells and weight stacks. Magnetic PlateMates allow the user to utilize smaller weight jumps while lifting weights thus reducing the risk of injury to muscles, tendons and joints. A Pair of PlateMates is for ONE Dumbbell only. Be sure to order Two Pairs of PlateMates for TWO Dumbbells (a pair). PlateMates must come in direct contact with metal for an ultimate hold. PlateMates will not "stick" properly to surfaces that are coated with rubber, urethane, vinyl, neoprene or any other coatings that inhibit magnetic attachment. PlateMates have protective coating on the outer surface (opposite from magnets) so they do not scratch dumbbells, equipment, or each other during use or storage. 2.5 lb. Donut PlateMates can also be used on hex dumbbells of 20 lbs and higher.