Wireless controller unit for the e ttl wireless autoflash system this master control device for a wireless speedlite flash system meets professional and advanced amateur standards its dedicated transmitter controls up to 3 canon speedlites as slave units 33 feet away outdoors and 495 feet away indoors it is mounted as a clip on with a shoe lock lever and locking pin wireless controller unit for the e ttl wireless autoflash system controls up to 3 canon speedlites as slave units 33 feet ran