there's no absolute way to measure a last (shells are not straight, they are curved and contoured), it's unfortunately confusing and complicated to measure- it's a lot like boot flex indices. When the SPK first came out, it had a claimed 105mm forefoot width. Salomon later stopped naming it as such because it scared a lot of people away from it. FT/Raichle was originally 98mm, but changed it to a 99mm. They didn't make it wider just probably changed how they measured the last. The point is, it's never absolute plus each 98mm boot has different shapes and contours which make them fit differently. Use it as a guideline and go from there.