Yongnuo Rf-603 C3 2.4ghz Wireless Flash Trigger/wireless Shutter Release Transceiver Kit for Canon 1d/5d/7d/50d/40d/30d/20d/10d Series Works as a wireless shutter release control to trigger your camera Transceiver System - works as a wireless flash trigger and receiver Each RF-603 is designed to work as trigger and as receiver Compatible with Canon 1D/5D/7D/50D/40D/30D/20D/10D Series cameras for shutter release control Includes (2) RF-603 transceivers (1) C3 shutter release cord