The Rumparooz One Size Cloth Pocket Diaper is four diaper sizes in ONE diaper. The Rumparooz will fit most babies at any size between birth (size newborn, 6 lbs) up through potty training (size large, 35+ lbs). Rumparooz are uniquely designed to grow with your baby. Your baby can wear the Rumparooz home from the hospital and later can wear Rumparooz while potty training! No additional sizes to purchase as your baby grows – one size fits most babies at all stages!