The NUK Happy Days Soother has an approved orthodontic shape which adapts to the shape of the baby's mouth and helps exercise the lips, tongue and facial muscles, promoting healthy development of both teeth and jaws. The flat shape of the soother helps prevent pressure marks and avoids being displaced from baby's mouth. The NUK Air System helps to ensure the mouthpiece remains soft and flexible, and the integrated grooves enable saliva to flow away from baby's mouth, preventing skin irritations to the area. Size 1 is suitable for babies aged 0-6 months. Approved by British Dental Health Association.