RF-603 II, the manual Flash trigger and shutter release ( you can use those two functions simultaneity ), it adopts a global free FSK 2.4GHz wireless channel which can be suitable in many countries. RF-603 II with FSK system, can be more effective to guarantee speed, distance and stability. Within capacious areas, the remote control distance may reach to 100m, and is suitable for the first generation RF-603.Suit for first generation, you can use them together.Note: Canon cameras choose RF-603 II Canon version, Nikon Camera choose RF-603 II Nikon version, other cameras can choose any version.