This medical id is made of 316L stainless steel which is not only hypoallergenic, but also non-corrosive. Plus, there is a variety of size selections, allowing for the perfect customized fit. The optional safety clasp, also known as sister hooks, is designed to protect those who may try to remove their medical ID. The clasp cannot easily be taken off without another-s assistance, making it ideal for someone with epilepsy or autism. NOTE: Select your size, then you will be prompted for the color choice and then clasp type.