The quantum qflash trio qf8c combines a qflash head with built in freexwire ttl radio and qttl adapter for your canon digital camera. Slip it onto the camera hot shoe, connect a turbo battery and you're ready to start shooting. The trio's radio trigger sends ttl commands to other remote qflash trio's. You can configure distinct modes and settings of remote qflash trio's from the on camera trio. In addition the on camera trio can remotely control an unlimited number of older qflash unit models mated to freexwire receivers. Radio qttl signals from trio do not require line of site like camera optical links... They're more reliable and will work at 5 times the distance. Qflash trio has all the same features as other qflash models including manual, auto, auto fill, ttl, strobo and program pre sets modes. Trio is powered by quantum's line of turbo battery packs. Some older qflash models require updates for certain features. Visit qtm.com for upgrade possibilities