Pack of 25 RFID Blocking Secure Credit Card Holder Id Card Anti Theft WaterProof Protector Secure Holder Water, weather and tear resistant, Prevents electronic pick-pocketing. Size: 3.62" x 2.48" (9.2cm x 6.3cm). Material: Metal Shielding Aluminum. Aluminum ferrules can avoid bank card, the second generation ID card, information card, social security card and other magnetic disappear or information leakage. Shields contactless credit cards, enhanced drivers licenses and many transit cards. A easy way to check whether they work or not: you can put a access card into this holder, then close to the access control deviceif the door can't be openedthat mean it can work. I once tryedand they are work