Neewer 16 Channel Wireless Flash Trigger Set: 1 Transmitter + 3 Receivers + 1 Sync Wire Cable for Canon, Nikon, Pentax, Sigma, Vivitar and Other Flash Units with Universal Hot Shoe Operate frequency: 433MHZ Sync speed: 1/250s Screw mount on receiver: 1/4" This flash trigger device is control discreteness for camera to trigger hot shoe flashgun synchronously. It's made up of two parts named signal transmitter and receiver. Work through wireless remote signal controlling. Very low voltage working. So it can ensure high level of safety and no damage to the camera.