Descriptions: Realize wireless optical and radio flash control function: In optical transmission and wireless radio transmission flash shooting, the YN600EX-RT II can used as master unit to control the flash mode, exposure compensation, flash ratio, number of stroboscopic and stroboscopic frequency.  Compatible with (for) wireless radio RT system: In wireless radio transmission flash shooting, cooperate with the YN600EX-RT(II), (for) 600EX II-RT/430EXIII,one YN600EX-RT II can used as set-top master unit or remote slave unit, totally 15 channels for option, realize TTL, manual flash and stroboscopic flash.  Supports (for) optical transmission wireless master flash: In the optical transmission flash shooting, the YN600EX-RT II can be used as master unit to trigger the and (for) EX series flash (excluding the YN585EX),supports 4 channels, realize wireless TTL, manual flash and stroboscopic flash.  GN60atISO100, 200mm: YN600EX-RT II as professional creative high guide number speedlite, supports TTL, M, Multi flash. Supports High-speed Sync: The YN600EX-RT II can realize TTL, manual flash, the highest shutter synchronous speed is up to 1/8000. Ultrafast Charging Recycle System, Supports External Power Supply: It just take 2 seconds at full output. Even if not use the brand new batteries, it just takes 3~4 seconds ultra-fast time to recycle; besides, you can also use the external power supply to meet your higher requirement.  Supports Firmware Upgrade: The YN600EX-RT II equipped with USB interface, supports firmware upgrade, you can download the upgrade firmware through the official website to upgrade the flash. Support Auto/Manual Zooming: Supports auto and manual zooming, the flash coverage can be changed between AUTO, 20~200mm. Multiple Trigger Mode Supported: The YN600EX-RT II can be triggered by the camera set-top, PC synchronous trigger, wireless optical/radio remote trigger.  Settings save Automatically, Supports Custom Settings (Fn).  Equipped with Big Size LCD Display Screen, Standard PC Synchronous Interface.  Specifications: Circuit design: Insulated Gate Bipolar Transistor (IGBT);  Guide No.