YONGNUO YN600EX-RT Auto TTL HSS Flash Speedlite with Radio Slave for Select Canon Cameras The YN600EX-RT can be used as on-camera master unit and remote slave unit of Canon's RT system,and supports Gr grouping mode. Fully Compatible with YONGNUO YN-E3-RT,Canon's 600EX-RT/ST-E3-RT Wireless Signal GN60@ISO100200mm;supports high-speed sync TTL, manual flash, Gr grouping flash, the highest synchronous speed can reach 1/8000s The YN600EX-RT supports YONGNUO, Canon's and Nikon's wireless optical master signal, supports S1 and S2 pre flash cancel mode. The YN600EX-RT supports auto and manual zooming, the flash coverage can be changed between AUTO, 20~200mm.