Evilbay. FYI, I can't speak for the 30 or 110, but i have a 20, 50, and 70. If I remember correctly, the 50 size is exactly 1/2 the 70 size, and the 20 size is 1/2 the 50 size. So a single 70 pad can be cut into 4 20 pads. In any case, get the big ones, and you can cut them down to size (they cut very easily and exactly with a sharp knife).