Fridge quality magnets are used on my designs.The magnet will be super glued to the printed model. Some designs will show up in the 3D viewer with hallowed spot for the magnet, others will just have a flat base area, depending on what is required for the design.
Ferrite – Dark grey, generally the size of a 4 stacked dimes. Holds light items.
Neodymium – Silver, usually a smaller, stronger magnet. Holds heavier items.