The aluminum foil ferrule can effectively prevent the information in the card from being maliciously stolen, prevent strong static interference and prevent the electromagnetic field from being damaged. Attached to the back of the phone, the information in the protection card is not degaussed. It is slim enough to fit into credit card slots in wallets, handbags, travel bags and smartphone cases. Water, tear resistant: Enduring resistant material to stand tears and punctures. suitable for daily use. They're even waterproof, so you don't have to worry about them. 2 7/16" L x 3 5/8"W