A great deal on great magnets. These neodymium ring magnets are .711" OD x .125" thick, .375" ID (17mm OD x 3mm thick, 10mm ID). Great for doing magnetic levitation, making magnet structures or just making absolutely sure that your shopping list will stay on your refrigerator...during an earthquake. Each package contains fifty of these amazing magnets.Note: All Rare Earth magnets, such as neodymium magnets, are made of a ceramic and can be brittle. They are extremely strong magnetically must be handled with caution to avoid damage to the magnets and/or injury. Fingers can be pinched between attracting magnets and magnets can chip or break if allowed to 'jump' at an attracting surface or another magnet. Close adult supervision is required.