United Kingdom Size Original to US: Super Snug / 45mm

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: Super Snug / 45mm: Corresponds to a nominal width of 45 $\text{mm}$ (1.77 $\text{in}$), length of 160 $\text{mm}$ (6.3 $\text{in}$), average structural girth of 90 $\text{mm}$ (3.54 $\text{in}$), and fit category Extra Small / Pediatric / Snug.