EveryOne-Buy 10PCS Anti Theft Credit Card Holder Protector RFID Blocking Aluminum Safety Sleeve Shield Radio frequency identification (RFID) is a technology that uses communication via electromagnetic waves to exchange data between a terminal and an electronic tag attached to an object for the purpose of identification and tracking RFID sleeves prevent electronic pick-pocketing;Size: 3.62" x 2.48" (9.2cm x 6.3cm) Sleek silver design slides into your wallet, purse, or card-holder with ease Neutral color and inconspicuous design, water-resistant, puncture and tear-resistant Can hold credit cards, debit cards, subway cards, driver's license, US resident green cards, etc.