United Kingdom Size Super Wide to US: Small / 51mm

United Kingdom Size Super Wide: Corresponds to a nominal width of 64 $\text{mm}$ (2.52 $\text{in}$), length of 215 $\text{mm}$ (8.46 $\text{in}$), average structural girth of 128 $\text{mm}$ (5.04 $\text{in}$), and fit category Extra Extra Large / Super Wide.

US: Small / 51mm: Corresponds to a nominal width of 51 $\text{mm}$ (2.01 $\text{in}$), length of 180 $\text{mm}$ (7.09 $\text{in}$), average structural girth of 102 $\text{mm}$ (4.02 $\text{in}$), and fit category Small / Regular-Narrow.