we're doing it again. The RadioPopper X system represents a highly scalable hardware platform that will grow with you. The new X series units were designed using the same radio hardware, so they all play nicely together. You may now seamlessly mix sophisticated ETTL/iTTL automatic flash including ratios and groups, with manually controlled lights or studio lighting units - at the same time, in the same image. Both of the new transmitter units are capable of manually adjusting power levels on both of the new receiver units. All of the units have been completely redesigned from the ground up to provide a reliable radio link on one of sixteen individual frequency channels, while providing an incredible usable range of 1700+ feet.