Although Gadgets & Stuff is based in the USA, the suppliers may use metrics to measure the sizes of the products sold on these pages. I have found 2 charts that will be very useful. I tried to find the ones that had no advertisements. I can't tell you that I was successful, but I tried. :-)

Here are the 2 charts that I find to have the most important measurements that might be found on these pages. Both chart in a format that is easy to use:

SHOE SIZE CONVERTER CHARTS --> https://www.shoesizingcharts.com/

CONVERT CENTIMETERS TO INCHES  --> https://www.unitconverters.net/