Our original elastic ZOX are about 175mm in length. Since the straps are made out of a buttery-soft elastic, the more you wear them the more they will stretch out to fit larger sized wrists.
Imperials are individually sized. You can find the size charts on the product pages. However, since you're already on this page, I'll include the printable chart here.
When you print it off, please be sure to follow the directions on the page so that it'll be as accurate as possible.