The round format is optimal for attaching to round things - if you have something in a square shape

You get a bag with 10 colorful magnets that look like push pins for a notice board

Large ferrite magnet with a hole in the middle

A4 blue magnetic foil

and because it's so flat

Power magnet, Blok 10x10x2 mm. 3M The round format is optimalNeodymium magnets Powerful magnets Length: 1 cm Width: 1 cm Height: 0. 2 cm Strength: approx. 1 kg. Flat, square power magnet with incredible strength. This size of power magnet is not suitable for glass boards. SPECIFICATIONS: Strength: approx. 1,000 g. Material: NdFeB Magnetisation: N45 Gauss: 13200 13700 (1. 32 1. 37 T) MGOe: 43 45 Max. temperaturee: 80C Surface: nickel plated (Ni Cu Ni)