These are great sleepers, but my 4 month old (14 lbs and 27 inches) wears a 12 month size.  We only bought one pack of 12 month and 2 18 month packs.  They DO shrink in the dryer.  One of the sleepers is made of a very nice heavy fleece and the other feels a bit cheaper.  I do like how the zipper goes all the way down the leg.  It makes it a snap to change a diaper in the middle of the night in the dark.  Best advice: order at least one size up.