US: Original / 54mm to United Kingdom Size Standard

US: Original / 54mm: Corresponds to a nominal width of 54 $\text{mm}$ (2.13 $\text{in}$), length of 191 $\text{mm}$ (7.52 $\text{in}$), average structural girth of 108 $\text{mm}$ (4.25 $\text{in}$), and fit category Standard / Original Universal.

United Kingdom Size Standard: Corresponds to a nominal width of 52 $\text{mm}$ (2.05 $\text{in}$), length of 185 $\text{mm}$ (7.28 $\text{in}$), average structural girth of 104 $\text{mm}$ (4.09 $\text{in}$), and fit category Standard / Regular.