Steel magnet cups and washers increase the power and versatility of already super useful rare earth magnet discs. The configuration of the cups generally increases the holding power of rare earth magnets by as much as 4 times. The steel washers compliment the cups by acting as the perfect strike plate. All cups and washers are countersunk to be screwed in, except for the 1/4" cup, which is barbed for a press fit. If you anticipate a need to remove the magnet at some point, you can simply file a notch in the side of the cup to provide a pry point to lift it out. Zinc plated steel. Imported Specifications #47297 Cup - Accepts a 1/4" magnet, has a cup O.D. of 3/8", and is barbed for a press fit for installation. NOTE: Cups and washers are NOT magnetic.