Phottix Strato II Wireless Flash Trigger Multi 5-in-1 Set for Canon - Transmitter and Receiver (PH15651) 4 groups: A,B,C,D 4 Channels 150+ m range 1/250 sec. sync speed Flash wake-up functions Remote control for studio strobes-speedlights-camera 2.4 GHz offers a range of over 400ft Pass through hot shoe transmitter allows TTL controll 4 channel in 4 groups Flash wake up system on receivers