The R-D1 is taller, wider and thicker than my R3A (AFAIK the same size as the R4x) by about 7-8mm in every dimension. It is also heavier. The big rechargable battery I think is the reason for taller and wider, and the LCD screen is responsible for thicker. The thicker body is what I notice most when using the R-D1 - not objectionable, but I really feel it when switching from a film RF.