http://www.yixingmagnetic.com/neodymium-magnets/

A neodymium magnet ring is a type of magnet made from neodymium, iron, and boron, which are some of the most powerful magnetic materials available. Neodymium magnets have a wide variety of applications, including in electric motors, hard disk drives, wind turbines, and magnetic separation equipment. The ring shape of the magnet allows for a more uniform magnetic field, making them useful in devices that require precise magnetic fields, such as speakers and MRI machines. Neodymium magnet rings can be found at many industrial supply stores or online retailers.
China Neodymium Magnets factory
website:http://www.yixingmagnetic.com/neodymium-magnets/