Seriously undersized. Order a size larger. (In my struggles to get it over the shoe, I broke off one of the pull tabs.) Also, contrary to the description, it DOES have zippers!
The pluses: very warm, and I think they made an effort to create a quality product. I might recommend this product, but would insist on ordering a size up.
Bought an XL rated for up to size 48. Tore off the heel pulling trying to pull bootie onto a size 47 road shoe. I was never able to stretch the bootie over my shoe because of the enclosed heel. Bought comparable Pearl Izumi and they fit great.