These white diaper cover bloomers are made of 65% polyester, 35% cotton batiste. Seat and legs trimmed with embroidered eyelet edging. Inserted waist elastic for babies and infants. NOTE: Diaper covers are sized to fit over diapers so are typically a little larger fit than you might expect from non-diaper cover panties. Typically, NB should fit birth to 3 months, SMALL should fit 3 to 6 months, MEDIUM should fit 9 to 12 months, LARGE will fit like 18 months, and XL will fit like 24 months.