POWERTEC 17100 Nylon Twin Wheel Chair Casters with 7/16" x 7/8" Grip Ring Stem 5 Pack, Black Wheel diameter: 2-inch (50mm) Wheel material: black nylon Mounting: grip ring stem - 7/16 inch diameter x 7/8 inch long Capacity: 75 lbs. Each 5 pieces in the Package