Maybe more size than I needed?
I ordered these larger pads to cover my back pain (lower spine).  The only problem I can report is that these pads really do cover a large area and you need to space them far enough appart, so that they don't interact with each other.  When I used them on my leg, for nerve pain, I had one on top of the leg and the other on the side and a little set back... this was ideal.  It's hard to get the spacing on the lower back, but I imagine that is you placed one lower and the other up and away from it that they would function well.
Rating: 3 stars