US: XS to Europe Size 56-21-150

US: XS: Corresponds to a lens width baseline of 46 $\text{mm}$ (1.81 $\text{in}$), bridge width of 16 $\text{mm}$, temple arm length of 135 $\text{mm}$, and fit classification Narrow / Petite Frame.

Europe Size 56-21-150: Corresponds to a lens width baseline of 56 $\text{mm}$ (2.2 $\text{in}$), bridge width of 21 $\text{mm}$, temple arm length of 150 $\text{mm}$, and fit classification Extra Wide / Oversized Frame.