100% Cotton! These are 100% cotton and nice and thick like the old-fashioned brands - not like the supermarket kind. Stretchy for easy dressing. You'll love them. Round neck for comfort and style. True to size. Double stitched for extra durability. Sleeve edges are finished with an interlock binding. Made of 100% ringspun interlock cotton for extra softness. This garment is not fire retardant and is not intended to be used as sleepwear. Made in England. Age/Size Weight Height 0-3 Months 10 lbs. 19-22 inches 3-6 Months 14 lbs. 22-25 inches 6-12 Months 18 lbs. 25-28 inches 12-18 Months 23 lbs. 28-31 inches 18-24 Months 27 lbs. 31-34 inches 24-36 Months 31 lbs. 34-36 inches