The PocketWizard FlexTT5 Transceiver Radio Slave is part of an ultra-versatile radio slave system, and is dedicated specifically to the Canon E-TTL II flash control system. It simply slides directly into the camera's hot shoe, and there are no special settings to make or modes to call up. Use the camera, on-camera flash, or flash commander controls for flash compensation, zone and ratio control. It supports single or multiple dedicated flash units.The FlexTT5 is the ideal addition to most Canon E-TTL II flash system. Since this system works on digital radio technology, it can support E-TTL operation around corners, out-of-sight, or in bright sunlight.The FlexTT5 is a "Transceiver", meaning it can be used either as a transmitter when placed into the camera's hot shoe in combination with another FlexTT5 unit on the flash end, or as a receiver with a MiniTT1 transmitter-only unit placed on the camera's hot shoe.