YongNuo have announced the YN660 speedlite, being the latest evolution in the very popular YN-560 range of manual speedlites, with recent models providing 2.4GHz remote manual radio transceivers built inside.
The YN660 build upon the previous YN560 IV, now providing 6 groups in the Radio Master mode, up from just 3 previously.
As well as boosting power output to a Guide Number of 66 meters (ISO 100, 200mm), which should now bring the YN660 fairly close to matching the top end Canon and Nikon Speedlites for output.
Other improvements include 20-200mm flash head zoom, lever locking foot, and updated buttons / main control dial.
The YN660 are basic manual only speedlites when used on camera. Though their main features / functions are the remote manual Radio Master and Slave modes.