YONGNUO Wireless Shutter Release & Flash Trigger RF-603II C3 for Canon DSLR 1D /1DS, EOS 5D Mark II/5D /7D/50D /40D /30D /20D /10D Wireless Remote Shutter Release ( On camera )--- You can mount one receiver into the camera and connect it with the camera via the 2.5mm shutter connecting cable, and can remote control the camera with other receiver. You can use it to fulfill the function of Auto-Focus, Continuous shooting, Long Exposure, Half-Way Pressing, Full-way Pressing and Bulb. Remote Shutter Release ( off Camera )--- You can use the single receiver to fulfill the function of remote shutter release after you connect it with your camera via the 2.5mm cable To fire the Flash Speedlite --- one receiver can fire one flash speedlite, one set of RF-603 can control 2pcs Flash Speedlite at the same time. The highest flash sync speed up to 1/320 second (some of models may only reach to 1/250s or less, difference combination of models of flash and camera using may achieved difference flash sync speed). Adding the Locking rings. Improved Flash / Shutter control Buttons. Working for more non Canon/Nikon cameras and single firing pin cameras.