These chrome steel baby moon hubcaps snap to the inside of our 15" Smooth Steel Wheels, #s 910-01560, 910-01580, 910-01510 and other similar smoothie wheels that have small bumps on the inside of the wheel center. The hubcaps snap in the center of these type of wheels. Please note that these hubcaps are not applicable to any other type of wheel other than the type mentioned previously. Caps are 8-1/4" O.D. Mount Flange (back side of caps) is 7-5/8" Chrome hubcaps. Set of 4.