Rare earth magnets are recognized for their superior magnetic force and sheer holding power, and these magnets are true to their word. Use for small lidded boxes, cabinet doors, or applications where normal lid or door closing hardware is aesthetically unappealing. Our washers and cups are all countersunk for use with flat head screws, the 3/8", 1/2", and 5/8" are packaged with ten #4 x 1/2" screws and the 7/8" and 1- 1/8" are with six #10 x 5/8" screws. The exterior of the 3/8" cups which have a ribbed outer surface designed to be press fit or glued into a 3/8" x 1/4" deep hole. All measurements given are outside diameter (O.D.) and represent the counter bore to fit the magnets, washers, or cups.