I wear a size 14 (EU48) and the XXLs easily slipped over them to keep my feet dry. They do not breath well so your feet can sweat. They keep the wind off on cold days too. I've cut a piece of fleece to put over toes between the shoe and the liner to give some breathing room and will add to this review after I try it.
UPDATE: After using these for part of the winter here in Colorado I'm quite happy with the performance. Keeps my feet dry and warmer. On really cold days I added a small piece of fleece between the shoe and the shoe cover (on top of toes) as layer of breathable insulation that really helps the feet from sweating and then getting chilled.;
