The Quantum Qflash Trio QF8C combines a Qflash head with built-in Free Xwire TTL radio & QTTL adapter for your Canon digital camera. Slip it onto the camera hot shoe, connect a Turbo battery & youre ready to start shooting. The Trios radio trigger sends TTL commands to other remote Qflash Trios. You can configure distinct modes & settings of remote Qflash Trios from the on-camera Trio. In addition the on-camera Trio can remotely control an unlimited number of older Qflash unit models mated to Free Xwire receivers*. Radio QTTL signals from TRIO do not require line-of-site like camera optical links... theyre more reliable & 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 & Program (Pre-Sets) Modes. Trio is powered by Quantums line of Turbo battery packs. * Some older Qflash models require updates for certain features.