The lens is not exactly a pancake but it's not all that big either. I always thought that the Sigma lenses worked better on the Nikon mount and now I know they work pretty well on the Nex mount too. Hmmm...I wonder what they`re like on the m4/3 mount. But then again I've got the Oly 17 f2.8 and the Panasonic 20 f1.7 and the PL 25 f1.4. So I don't think I need them for that mount but Sony is lacking in this area and I'm glad Sigma decided to bring this one out.