United Kingdom Size 20G Standard Stud to US: 16G Piercing Standard

United Kingdom Size 20G Standard Stud: Features a post thickness of 0.8 $\text{mm}$ (0.0315 $\text{in}$), hoop inner diameter of 0 $\text{mm}$, gemstone carat equivalence of 0.25 ct - 0.50 ct, and earring style Stud / Minimalist.

US: 16G Piercing Standard: Features a post thickness of 1.2 $\text{mm}$ (0.0472 $\text{in}$), hoop inner diameter of 0 $\text{mm}$, gemstone carat equivalence of 1.50 ct+ / Bold, and earring style Stud / Cartilage.