United Kingdom Size Original to US: Classic Regular / 53mm

United Kingdom Size Original: 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.

US: Classic Regular / 53mm: Corresponds to a nominal width of 53 $\text{mm}$ (2.09 $\text{in}$), length of 190 $\text{mm}$ (7.48 $\text{in}$), average structural girth of 106 $\text{mm}$ (4.17 $\text{in}$), and fit category Standard / Original.