It is a rewritable RFID card with 330 bits of storage capacity The T5577 chip allows for both normal mode and enhanced mode operation It has encryption capabilities and anti-collision features Typical applications include access control, attendance tracking, payment systems, etc. It can be read from 5-10 cm away The card data can be rewritten over 100,000 times Data is rated to be retained for 10 years The cards come in a package of 20 white PVC laminated cards The important note is that these cards ship blank, so you need to write data to them first before they can be read by compatible RFID readers/writers. The intended use case seems to be for cloning/copying data from other compatible 125KHz RFID chips/cards onto these T5577 cards.