Selling set of 4 used Wireless Flash Triggers. Under-utilized, hence selling. Highlights: Compatible with Canon E-TTL / E-TTL II Support for 622 and 560-RX Communication Frequency: 2.4 GHz Range: 328' TTL and Manual Flash Modes Supports Group Ratio & Multi Flash AF Assist Beam; USB Update Support High Speed, 1st and 2nd Curtain Sync PC Sync Port and Super Sync Function Runs on 2 AA Batteries Features: Trigger flashes wirelessly with this 2-pack of YN-622C II E-TTL Wireless Flash Transceivers from Yongnuo. Compatible with Canon E-TTL / E-TTL II cameras and with added support for 622 and 560-RX communication protocols this set will function well with many flash units. For usage, one transceiver slides directly into the hot shoe and utilizes a 2.4 GHz frequency with a range of 328' to trigger the remote flashes mounted on the other transceiver. A variety of features have been added in the model, including support for group ratios and multi flash. The transceivers also have a hot shoe and PC sync port available for mounting a flash unit or connecting to a strobe. When connected to a strobe via the PC sync port, a Super Sync function will allow photographers to achieve a faster sync speed than normally possible with their camera. Additionally, there are both TTL and manual flash modes available for full creative control. And, it can utilize 7 channels and 3 groups for setting up multiple flash units easily and efficiently. The YN-622C utilizes a series of LEDs to display settings and allow users to make adjustments. On the device is also an AF assist beam to help in low-light conditions. Multiple sync modes are available for more specific needs or effects, including 1st 2nd curtain sync. A high speed sync mode is available and will help in bright lighting conditions and for stopping motion with a maximum speed of 1/8000 second. Additionally, the transceivers run on 2 AA batteries each.