These are SUPER strong neodymium magnets. They are disk shaped with a 15mm (0.59") diameter and 5mm (0.2") thick. We use these to build our larger sized magnetic ledges. and a single pair can EASILLY attract each other through the glass or acrylic of normal enclosures and if you need even more holding power, they can simply be stacked to increase the magnetic force proportionally.
Note: price is per individual magnet.