"What size skis should I buy?" That is one of the most commonly asked questions we receive here at Proskiguy. And, the answer to it is not always easy for us to offer. It depends on a lot of factors; size, skill, preferred terrain, and more. But, there is one set of numbers that can often provide a good first hint. And those numbers are the sizes that the particular ski is offered in.
For instance, compare two skis, from the same manufacturer that are approximately the same width. Nordica Enforcer 93, and Nordica Navigator 90. The E93 comes in 169, 177, 185, 193 and the N90 comes in 165, 172, 180, 186. As you can see, at the bottom of the range, the shortest sizes are pretty close (165 vs 169). But, at the top of the range, there is almost one full size difference (186 vs 193).
So, a good way to consider this would be to assign a generic S, M, L, XL to each of the four sizes offered. Then, categorize yourself. Which of these sizes best describes you? A 5-10, 190 lb guy would most often be a large for instance when choosing clothing. So, in the Enforcer he would be on a 185, but, in the Navigator, he would be on a 180.
This assumes that you are choosing the ski that best suits you, and where you will be skiing. Such as, the Navigator is more targeted at majority on trail use, so it has no rocker in the tail, and not nearly as much extended length at the tail. Enforcer is more off trail oriented, with much more rocker in the tail, and a totally different tail shape.
So, the point of this is, paying attention to the sizes the ski is offered in gives a clue as to how the manufacturer has designed the sizes to be used. On some skis, the size will be shorter, and on some it will be longer. But, S, M, L, XL is a good way to begin the discussion regarding proper size for a particular ski.