The Photogenic RTK-4 Radio Trigger Set enables firing of a StudioMax III or any other strobe monolight or power pack, without running a sync cord between the camera and your flash unit.This four-channel system is designed for use with both portable off-camera flashes and studio strobes. It provides reliable radio technology to trigger strobes up to a distance of 150' (50 m) without sync cords or unreliable optical slaves. Add a receiver for each additional flash unit in your set up.