S: newborn up to 4 Month ( 0 - 14 pounds)
M: 3 Month up to 10 Month ( 12 - 18 pounds)
L: 9 Month up to 22 Month ( 16 - 24 pounds)
XL: 20 Month up to 5 years old or 6 years old ( 22 - 47 pounds )
if your baby age between 2 size please pick larger size