high guide number of GN66. Supports wireless master control function, realize six groups of light control. And supports wireless slave function, accept the signal transmitted fromYN660,YN560IV,YN560-TX,RF605,RF605,RF603(II) and RF602, when the YN660,YN560IV and YN560-TX used as transmitter, it can realize remote flash parameter adjustment. Features: Support 2.4G wireless transmission, controllable distance up to 100m. High guide number of GN66, ultra fast recycle time up to 3s. Multi trigger mode: on-camera/TX/RX/S1/S2. A master control unit: realize remote control the flash mode, output and focal length of YN660,YN560IV or YN560III. A slave control unit: accept the signal transmitted from YN660,YN560IV,YN560-TX,RF605,RF605,RF603(II) and RF602, when the YN660,YN560IV and YN560-TX used as transmitter, it can realize remote flash parameter adjustment. Supports 16 channels and 6 groups. Support electric zooming function, sound prompt, automatically saving setting, power saving mode, over-heat protection. Specifications: Curcuit Design: IGBT; Guide No.: 66(ISO 100, 199); Flash Mode: M/Multi; Trigger Mode: Camera set-top/TX/RX/S1/S2; Zoom Range: 20mm/24mm/28mm/35mm/50mm/70mm/80mm/105mm/135mm/199mm(199mm is equivalent to 200mm focal length); Vertical Rotation Angle: -7-90 degrees; Horizontal Rotation Angle: 0-270 degrees; Power Supply: 4 * AA(Not included.); Lighting Times: 100-1500 times; Recycle Time: Approx.3s; Color Temperature: 5600K; Flash Control: 8 levels of output control(1/128-1/1), 29 levels of fine tuning; External Interface: Hot shoe, PC port, External charging port; Wireless Triggering Distance: Optical--20-25m(indoors)/10-15m(outdoors); 2.4G--100m; Additional Features: electric zooming function, sound prompt, automatically saving setting, power saving mode, over-heat protection, advanced options setting; Item Size: 21 * 6.5 * 5cm / 8.3 * 2.6 * 2.0in; Item Weight: 427g / 15.2oz; Package Size: 22 * 10 * 9cm / 8.7 * 3.9 * 3.5in; Package Weight: 613g / 21.6oz; Note: The batteries are not included. Package List: 1 * Speedlite; 1 * Carrying Pouch; 1 * Mini Plate; 1 * User ManualManual