We are often asked in the Showroom if Wellington Boots come in different widths.
Different manufacturers will use different 'lasts', or standard profile for the foot.
We were talking to David and Jan Foster about this recently.
In the case of Grubs Boots, they use a 'last' ref RBK84B - RBK stands for REEBOK and 84 stands for 1984. This can be traced back to David Foster's days at the family firm REEBOK which is detailed in the Grubs Boot Heritage web page.
Returning to the question, although there aren't different options in terms of width for the same boot, different styles will vary in terms of their width and how well they fit you. As is often the way with shoes, the only way to be sure of the fit is to visit a showroom and try on a couple of pairs to see what works for you.
I was also surprised to find out that in the USA, boots are narrower than in Europe - hard to think that Americans have narrower feet than Europeans, but that is the case.
There is always something new to learn about boots!