R09 is a new name for the famous Agfa Rodinal, now discontinued.

This liquid has very interesting proprieties which depend on its diluition in water.
So, if you use this delevopment liquid in a 1-25 solution you obtain sharp and pretty grain with high contrast (good effect with slow speed films as Ilford PanF or FP4 ), while a 1-50 solution is more compensating (good for example when you use an Ilford FP4 film in a bright day, to avoid excess of contrast).