The Ergobaby Adapt carrier adapts to your growing baby in just one step. First, adjust the seat using the velcro tabs on the waistbelt based on your baby's height: along the red lines for a baby between 20-24 inches / 50.8-61 cm (~0-3 months), along the yellow lines for a baby between 24-28 inches / 61-71 cm (~3-9 months), along the blue lines for a baby over 28 inches / 71 cm (~9 months +). Second, use the two straps on the front to further fine-tune the width of the seat at each stage to ensure your baby’s thighs are fully supported from knee to knee in an ergonomic M-shape position. For each seat position, you would usually start with the straps fully pulled and attached to the narrowest snap setting, and gradually release to the medium then widest snap setting as your baby grows to fully support her/his thighs. Third, adjust the head and neck cushion for proper support: folded on the inside and buttoned from the side to the lower buttons on the front for a tighter support for babies 6 weeks and under, folded on the outside and buttoned to the lower buttons for babies 7 weeks and up."