United Kingdom Size Extra Small to US: Slim / 49mm

United Kingdom Size Extra Small: 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.

US: Slim / 49mm: Corresponds to a nominal width of 49 $\text{mm}$ (1.93 $\text{in}$), length of 175 $\text{mm}$ (6.89 $\text{in}$), average structural girth of 98 $\text{mm}$ (3.86 $\text{in}$), and fit category Snug / Close.