Onya Baby Booster Infant Insert. The Onya Baby Booster is lightweight, breathable and securely snaps into your Onya Baby carrier. Its unique design comfortably cradles while allowing you to adjust the boost as your baby grows. A breathable outer layer under your baby's bum keeps them cool. The snap closure allows for height adjustability and ensures secure attachment to your Onya Baby carrier. Materials: 100% Organic Cotton French Terry Lining, Breathable Air-Mesh Exterior.