I knitted these this week. The pattern is my own, done on size 7 dpn. I allotted 2 balls of yarn to them but they only took one so I still have a ball to make a matching hat and booties :) They are a size newborn/ small. The bottom of the legs is 4" of ribbing, done so that they are totally adjustable in length. I would imagine they could accomodate a skinny baby for quite awhile, since they expand to 9" in length (for the legs, anyway).
Ok, off to knit some matching accessories!