Maybe you should refine your question a bit so we would know how to answer it better.
Today only a few models are still being made in the 84mm size by Victorinox, while for decades most of the lineup they offered was available in both 84mm and 91mm sizes. At some point in the late 70s early 80s if memory serves me right, I'm by no means an expert on history, Victorinox decided to concentrate on the 91mm size and Wenger chose the 85mm size and it remained like that till today.