Microloading with PlateMate® is the safe, scientific way to build strength at beginning, intermediate and advanced exercise levels. Ideal for saving money & space. Our 2.5lb Donut allows for the same benefit of owning a full rack of steel dumbbells for half the price.Attached to each end of a dumbbell, the 2.5lb donut allows for 5lb increments eliminating the need to buy every other pair of dumbbells. Which also saves you space. These magnetic add-on weights attach quickly and easily to ends of any iron dumbbells and stack weight machine plates. PlateMates are ideal for physical therapy where small increases help patients regain strength without overburdening injured muscles and tendons. SPECIFICATIONS Sold In Pairs Includes: (2) Donut Shaped Magnetic 2.5 lbs. each (5 lbs. total weight for pair) Dimensions: 4-1/2" (11.43 cm) outside diameter, 2-1/4" (5.715cm) inside diameter, 1-1/8" (2.858 cm) thickness Magnetic: Must come in direct contact with metal for an ultimate hold. They will NOT magnetically stick properly to surfaces coated with rubber, urethane, neoprene, vinyl. Patented Design: Works with steel or cast iron plates and dumbbells Protective Coating: On the outer surface (opposite from magnets) prevents scratching of dumbbells, equipment, or each other during use or storage. New Design: PlateMate® Donuts feature a new design and will NOW fit around Olympic Barbells. Intended for use with 25 lb dumbbells and higher. It is important to make sure your dumbbells are large enough to fit the 4"x4" magnetic surface area. Warning: Do NOT use PlateMates® with kettlebells.