Man, Nokia is a bunch of lazy ******. BP-4L is li-po vs li-ion for the BP-5J. They're the same thickness, and the 4L is only a tiny bit wider and taller. It could easily fit in the n900 or any other phone if they had wanted it to. The e71 is the smallest Nokia smartphone (thinnest) and it has the biggest size battery. No big deal. It doesn't need it, but nobody complains about the extra life. With meego or maemo we have some 3d accelerated multitasking OS, and they decide "lets just put a little battery, it's easier/cheaper/whatever". I don't know. Look at the picture, I have both on my desk. It's sad how close it is to fitting.