Permanent Magnets Ring Ndfeb Magnet
https://www.mlmagnet.com/product/ndfeb-ring-shape-magnet/powerful-permanent-magnets-ring-ndfeb-magnet.html

This Ring NdFeB Magnet is made from high-quality neodymium iron boron (NdFeB) magnet grade samarium cobalt (SmCo) and iron. These materials have the highest magnetic strength, more than 3 times higher than ordinary magnets. It is 5 times stronger than AlNiCo magnets.