Which frequencies choose between HF (High Frequency) and UHF (Ultra High Frequency)?

The choice of frequency depends on the application of the RFID technology and the environment envisaged. The HF frequency allows to read tags at a distance of about a few centimeters while the UHF frequency allow a reading at several meters depending on the environment.
HF technology remains highly disturbed by metal environments while UHF technology will get through with specific tags.