Specification 

• YONGNUO RF-603C-II-C3 Wireless Remote Flash Trigger Kit
  for Canon 1D 5D 7D 10D 20D 30D 40D 50D
  
• Adding the locking rings
• Max sync speed: 1/320 second
• 3.100m transmission distance with 16 channels
• Type: FSK 2.4GHz wireless remote control system
• RF-603 II with FSK system, can be more effective to 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 transceivers.
  It can be set to single transmit state(TX), which will be more convenient for testing flash and
  can 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 respectively.
  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-603C II x 2, LS-2.5 shutter cable x 1, Manual x 1.