The Yongnuo YN560 mk4 is a versatile manual wireless speedlite flash with built-in 2.4 GHz radio transmitter and receiver capabilities. Delivering a guide number of 190 at ISO 100 and 105mm, this flash is ideal for off-camera flash photography and studio work. The adjustable zoom head covers a focal length range from 24-105mm (expandable to 18mm with the included diffuser), and power output can be controlled from 1/1 to 1/128 in 1/3 and 1/2 EV steps. The flash head offers impressive mobility with -7 to 90 degrees of tilt and 270 degrees of rotation. Powered by four AA batteries, the YN560 mk4 delivers 100-1500 flashes per set depending on power level, with a quick 3-second recycling time. As this is a secondhand unit, please ensure it is in good working order before use.