Flash trigger This flash trigger device is control discreteness for camera to trigger hot shoe flashgun synchronously. It's made up of two parts named signal transmitter and receiver. Work through wireless wireless remote signal controlling. The transmitter is consisting of advanced designed circuit and component,and works through sending encoded signal. It comes with 2.5mm sync port,which permits the camera without hot shoe using this flash trigger.So,this flash trigger can work with all camera with stand hot shoe mount and those cameras with 2.5mm mm port.(but not work with Sony flashes) Very low voltage working make sure that high level of safety and no damage to camera. It is very useful when you want to trigger 2 flashes at one time. Specification: Operate frequency: 433MHZ Sync speed: 1/250s Work range: ?30M Screw mount on receiver: 1/4" Battery for tramsmitter: 23A-12V mini batter (the battery included) Batery for receiver: 2x1.5V AAA battery (the batteries not included) Suitable: Canon SpeedLite 580EX II, 580EX, 550EX, 540EZ, 520EZ, 430EX, 430EZ, 420EX, 420EZ, 380EX; Nikon SpeedLight SB-800, SB-600, SB-28, SB-27, SB-26, SB-25, SB-24; Pentax AF-540 FGZ, AF-360 FGZ, AF-400 FT, AF-240 FT; Sigma EF-500 DG Super, EF-500 DG ST, EF-430; Sunpak Auto 2000DZ, 622 Pro, 433AF, 433D, 383, 355AFm 344D, 333D; Vivitar 285HV (Older Vivitar 285/283 works only with PC sync); Other flash models with a trigger voltage of 12V or lower; Work with flash units using universal hot shoe like Nikon, Sigma, Olympus, Pentax (except Minolta SONY as they use a special hot shoe). Package Contents: 1x Transmitter (with built-in battery) 2x Receiver (AAA Batteries not included) 1x PC Sync cord for camera (2.5mm to Male)