Size chart here:
First off, I'll give the 5 stars because they are great quality and when you get a pair that fit, they fit brilliantly: nice and close to the boot and very easy to get on and off.
I think the neoprene cuff could be tighter and I also don't see the need for the height of it, but these are minor issues and certainly take nothing away from the quality of the product; just suggestions on how I think it could be better.
Now for the sizing. Do not use RC.com's size chart above. I have no idea what it even refers to but it's nothing to do with Gore footwear...they have never even made this in an XXL size and if they did it would only be a few guys with size 17+ feet.
One reviewer below posted a Gore size chart that is slightly more accurate however these things are big. I have 3 sets of shoes and they are all EU44 / US10's: a pair of Shimano MTB shoes; a pair of Mavic Road shoes and a pair of Keen Springwaters for commuting. The Large size is marginally too large. It specifies 42-44EU/8.5-10.5US on the tag, but no way, no matter how fat your feet are are these going to fit a 42 or, in my opinion, a 43.
So here's my size chart for these. Obviously buying online is tough as so many variables with diff shoes, but I think it's more accurate than anything published by either Gore or RC:
S = 39-41EU / 5.5-7.5US
M = 41.5-43.5EU / 8-10US
L= 44-46EU / 10.5-12.5US
XL= 46.5-48.5EU / 13 - 15US (I love the recommendations to buy this size below...pure gold)
If you have wide feet, you may add a half size for variance I figure as I have very narrow feet.