This Canon ST-E3-RT Speedlite Transmitter works great. It will Wirelessly trigger your compatible Canon Flash Units, like the 600EX-RT. IT POWERS-UP AND IS WORKING PROPERLY. THERE ARE LIGHT MARKS ON THE LCD SCREEN COVER, OTHERWISE: THE BODY IS IN GOOD CONDITION WITH LIGHT FINISH WEAR FOR PRO-EQUIPMENT. I AM GRADING IT AS EX/EX+ ...GOOD USED CONDITION.