Yongnuo Flash YN600ex-rt Wireless HSS 1/8000s Master Flash Speedlite for Cannon Camera YN600EX-RT can be used as on-camera master unit and remote slave unit of Canon's RT system and supports Gr grouping mode YN600EX-RT can be used as master unit to trigger another YONGNUO YN600EX-RT or Canon's 600EX-RT and live display the flash groupings of slave unit and recycling information. GN60@ISO100, 200mm, supports high-speed sync TTL, manual flash, Gr grouping flash, the highest synchronous speed can reach 1/8000s YN600EX-RT not only supports YONGNUO, Canon's and Nikon's wireless optical master signal, but also supports S1 and S2 pre flash cancel mode The YN600EX-RT equipped with the USB interface, supports firmware upgrade, the users can download the upgrade firmware through the Yongnuo official website to upgrade the flash