http://www.meank-magnet.com/products/permanent-magnets/pvc-magnetic-button/ The magnetic buttons(also called as button magnets) are made of thin neodymium magnets and steel cover,then sealed in soft PVC. The rare earth neodymium magnets provide the maximum magnetic strength.The steel cover are mostly made with Zn-plated to make it durable in wet condition. By using the hidden PVC magnetic button, the appearance of application products can not be affected.