This is one of the most important parameter defining one particular RFID technology.
The frequencies used for RFID purposes are regulated by the law, and are falling in what is called the ISM band (the set of frequencies allowed for Industrial, Scientific and Medical applications), which is regulated at national level - so different countries force different frequencies for the same application. So, while the LF, HF and the MW (with minor changes) ranges are universally standardised, the UHF range is not.
However, being the frequencies used for UHF in different countries very close, it is possible to find wideband tags working properly in different countries.
