I have purchased Fox River microfiber socks before and love their softness and durability.  The size descriptions are different depending on the color.  The medium fits me just fine (I wear a 7 or 8 womens shoe depending on style) and when they show a size it's a shoe size.  These socks are very soft on the skin.  If you have sensitive skin they are extremely comfortable with smooth toes and no irritating seams.  They are a great buy at this low price.