HF tags operate at 13.56 MHz giving a wavelength of approximately 22 meters which is much shorter than the 2200 meters of low frequency RFID systems. This frequency is available worldwide at adequate power levels, without special licensing. The radio waves will still pass through materials with the exception of metals. However, unlike LF systems, some energy is lost which results in reduced range. HF Tags mainly use a flat label format with etched flexible antennas. The magnetic field is still used to power the tag, so HF systems also have a well defined read zone. HF systems are also capable of reading multiple tags in a RF field simultaneously (up to 60 tags a second).