Speedlite Release Cable SR-N3
A cable that is required for some EOS *2 for remote release and interlock photography.
1. Radio transmission supported strobe products: Speedlite 600EX-RT Speedlight transmitter ST-E3-RT (as of March 2012)
E-TTL/E-TTL II automatic dimming compatible camera with EOS cameras other than 2EOS-1D X, EOS 5Ds R, EOS 5D Mark III, EOS 7D Mark II with N3 type remote control.