Features:
It includes all the features of ST-E3-RT, as well as extra features including USB port for firmware updates.
AF focus assist light.
Full GR Group Mode functionality has also now been added for pre 2012 model cameras.
Slave flash charge status does not stop other flashes from firing.

Specifications:
Type: On-camera Speedlite transmitter
Compatible cameras: EOS type-A camera compatible with E-TTL II/E-TTL autoflash
Exposure control system: E-TTLII/E-TTL autoflash, manual flash, stroboscopic flash, auto external flash metering (Only when teh flash mode is set to )
Modulation system: Primary modulation: OQPSK, secondary modulation: DS-SS
Frequency: 2405-2475 MHZ
Channel: Auto, Ch.1-15
Wireless radio ID: 0000-9999

Package List:
1 * Yongnuo Speedlite Transmitter YN-E3-RT
2 * Shutter Release Cable For Camera (C1 / C2)
1 * Manual (English & Chinese)
1 * Protect Bag