If you have a River 3+ and want an extra battery but have limited room, you may be interested in the difference of the size difference between the EB300 and the EB600. The holding capacity and weight difference between the two is obvious. Written dimensions are somewhat helpful, but sometimes not enough.

The EB600 is just under 5.5" tall - the same height as the River 3+, for a combined total height of just under 11". Pictures can be a bit deceiving and there may be the illusion that the EB600 is taller than the R3+, but they are the same height.

The EB300 is just under 3.5" tall, when attached to the River 3+ the combined height is around 9" tall.

Pictures in order:
1) Side by side comparison of R3+ with EB600 (L) and EB300 (R).
2) R3+ with EB300 in a stereo cabinet with 13" between shelves with laptop next to it
3) R3+ with EB600 in the same stereo cabinet
4) R3+ with EB600 running my laptop