We offer two chips:
The Mifare Ultralight chip is a smaller capacity that is NFC Forum Type 2 compliant. It will work with every NFC enabled device and can easily be made read-only.
The Mifare 1k chip is a robust prototyping chip, that is compatible with the Nexus S. It has plenty of space but cannot be made read-only.
If you have any questions, are ordering in bulk, or would like to customize your NFC stickers please contact us directly.