NXP Mifare Classic 4K Cards.

Sold in packs of 10, 20, 50, 100, 500 and 1,000.

The 1k refers to 4,000-byte memory capacity. The Mifare classic operates at 13.56MHz and offers a typical read/write range of 10cm. 

Gloss finish, suitable for overprinting on desktop card printers and a wide range of functions.