Just for a data point, I picked up a set of 2XL Eddy Fins recently. I wear a size 12 Hollis/Whites EVO hardsole boot, and the fin is just on the edge of being too big, but I suspect the XL might be too tight. There's a small amount of side-to-side slop in the heel, but the toe is snug and in the water there's no fin slop at all. Compared to my XXl Hollis F1 fins, the Eddy foot opening is larger, and it's a lot easier to slip on. Buoyancy is also slightly lighter which seems to help the trim. After one dive, it seems to be a nice fin.