The TDSi 2920-3003 Mifare 4K cards with serial number offer excellent access control options, perfect for a variety of applications. These cards operate at a frequency of 13.56 MHz and have a 4K-byte memory, making them ideal for secure access control. Furthermore, each card comes with a unique serial number, making it easy to issue and track.Product Features:Sold in packs of 100CR80 card size (86mm x 54mm)13.56 MHz operating frequency