Macro flash allowing to get the heads very close to the lens front element with very flexible adjustment. Mostly used with the MP-E and includes a feature where a double tap on the shutter button turns on focus assist lights. Only weakness is of course it is dedicated for macro and close-up use. However it does act as a master, does high speed and 2nd curtain sync. One problem is diffusion as there is little room between head and subject, one of the best solutions is provided by Ian McConnachie the UK. It is quite an expensive option though.