Yongnuo RF-603 II adopts a global free FSK 2.4GHz wireless channel which can be suitable in many contries. 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 suitable for RF-603 Mark I. Yongnuo RF-603 II wireless flash trigger kit is formed by two sam transeivers. It can be set to single transmit state(TX), which will be more convenient for testing flash, andcan be set to transceiver state(TRX), automatically switch transmit and receive state, adopts 2 levers button design, it will realize the awakening, flash testing, focus and shutter function in "TX" and "TRX" state repectively. Transmitter supports single contract triggering, supports wireless wakening up and triggering the flash through the camera hot shoe, with PC sync cable(optional) can be trigger studio lights, with specially camera shutter connecting cable can realize wired / wireless shutter release remote control, supports controlling multiple cameras and flashes at the same time. The highest flash sync speed up to 1/320 second (some of models may only reach to 1/250s or less, difference combination of models of flash and camera using may achieved difference flash sync speed). Specifications: Type: FSK 2.4GHz wireless remote control system Transmission distance: 100m Channels: 16 channels Shutter release: half-press, full-press Shutter interface: 2.5mm socket Studio flash light interface: standard PC socket Max Sync Speed: 1/320 second Battery: AAA x 2(3V) Include items: RF-603N II x 2 LS-2.5 shutter cable x 1 Manual x 1