Dimensions and How to Pick the Right Backpack

Small: Up to 9 lbs - 4 kg
            12 x 13 in | 30 x 34 cm
            Head Hole: 6.2 in | 16 cm

Large: Up to 18 lbs
            14 x 17 in | 36 x 45 cm
             Head Hole: 8.2 in | 21 cm