YN560 IV=YN560III+YN560-TX?? Supports Wireless Master Function.</br>Supports Wireless Slave Function?? fully supports YN560-TX?? RF-603 II RF-602 Wireless Transmitter.</br>Supports Multiple Trigger Synchronous Mode.</br>Supports setting save automatically?? custom settings ( fn ).</br>Supports ultra-fast charging recycle system?? External power supply.</br></br>Product Description</br></br>Specification: YN-560 IV Flash Speedlite is a combination of YN-560 III and YN560-TX???? it has built-in wireless trigger system?? so you can not only use it as flash