Canon ST-E2 Speedlite Transmitter for Canon 580EX II, 430EX, 430EX II Speedlites Wireless flash controller for the Canon 420EX and 550EX and other Canon flashes. Indoor transmission range of approximately 40 to 50 feet Outdoor transmission range of approximately 26 to 33 feet 1,500-transmission battery life Turns off after 90-second idle