US: 3-6M to Europe Size 49-51

US: 3-6M: Corresponds to a head circumference baseline of 42.5 $\text{cm}$ (16.7 $\text{in}$), neck circumference of 24 $\text{cm}$, shoulder width of 22 $\text{cm}$, and age range 3–6 $\text{months}$.

Europe Size 49-51: Corresponds to a head circumference baseline of 50 $\text{cm}$ (19.7 $\text{in}$), neck circumference of 30 $\text{cm}$, shoulder width of 28 $\text{cm}$, and age range 24–48 $\text{months}$.