A new 13mm HDX tag from Texas Instruments RFID that is available in limited quantities exclusively from Oregon RFID.
They are read-only tags with a 64 bit unique ID. ISO 11784/11785 compatible.
The size of the tag affects the read distance. Large tags such as 32mm glass transponders can be read at longer distance from the antenna since the internal coil intersects with more of the magnetic charge field. The 13mm tag will have a shorter range for a given antenna. The read range you obtain will depend primarily on the antenna.
Due to significant demand the tags were sold out in a few days. Another larger batch is due in a few weeks. Contact sales@oregonrfid.com for samples.