The RadioPopper PX-RC Receiver with Canon Mounting Bracket maintains the ETTL/iTTL functions of your camera and flash while adding radio triggering that can fire your flash at distances of 300 to 1,750' depending on the prevailing conditions. While the receiver is compatible with both Canon and Nikon flash units, this version comes with a Canon mount. When used with the required PX Transmitter on your master flash or commander, slave flash units equipped with the a receiver can get TTL or iTTL signals by radio which are then translated into IR commands without the limitation of having to be in line of sight with each other. Put simply, the RadioPopper enhances your ETTL/iTTL system by allowing it to act like a radio slave.