I bought the ABF Flip Flop and the ABF Single Flip Flop.  Due to the size descriptions of other reviewers, I bought a size 7.  My tennis shoes and other Croc Flip Flops are all size 8.  I have the Croc Athens, Crete, and Capri flip flops, however the size 8 in those flip flops are a little big on me.  I bought the ABFs in a 7 and they fit perfect.

The ABF Single was comfortable almost immediately.  It feels a little odd when you first put it on, but after walking around in them a few minutes they feel great.

The ABF flip flop is harder and less comfortable - at first. The longer I wear them the more comfortable they are getting.