Matfer Bourgeat 062009 Black Steel Round Frying Pan, 17 3/4-Inch, Gray

Q: What is the diameter of the cooking surface of your various size black steel frying pans. Not the overall diameter of the pan.

I don't know if they've recently changed the design of these pans, but I just got the 8 5/8" size and the diameter of the cooking surface (the INSIDE flat bottom) is only 5 3/4" not 6 1/8". I'll need to send this back for an exchange. Really wish there were full accurate measurements somewhere. By the way, I also have the 11 7/8" size and the cooking surface is 8 7/8", not 9 1/8". I suspect the measurements from Matfer are for the OUTSIDE bottom of the pans.