How to read the table
Read the table from top to bottom. In the example, the strap is 20mm at the lugs, which is the width of the strap at the watch, and 20mm at the buckle, which is the width of the strap at the buckle.
The thickness refers to the strap at the watch.
Side A is the part of the strap with the holes. Side B is the part with the buckle, measured without the buckle.
