Yongnuo Updated YN600EX-RT II Flash Speedlite for Canon's 600EX-RT/ST-E3-RT Wireless Signal Camera, Master,USB Firmware Upgrade, 1/8000sec Sync Speed Compatible with Canon E-TTL / E-TTL The YN600EX-RT II can be used as on-camera master unit and remote slave unit of Canon's RT system,and supports Gr grouping mode. GN60@ISO100200mm;supports high-speed sync TTL, manual flash, Gr grouping flash, the highest synchronous speed can reach 1/8000s The YN600EX-RT II supports YONGNUO, Canon's and Nikon's wireless optical master signal, supports S1 and S2 pre flash cancel mode. The YN600EX-RT II supports auto and manual zooming, the flash coverage can be changed between AUTO, 20~200mm.