What are "Super" Wools?
It's hard to go far in looking at men's fashion without coming up against the "Super" wools. Super wool is a trade name that traditionally described fabrics made of the finest wool available, typically merino wool (wool from the merino sheep). Nowadays the term can also be used for wool blends. The Super wool fabrics are classified with an S number that designates the fineness of the wool fiber, classified in microns. In the 1950's, wool suits were usually 70s and 80s. The finer fibers available with today's manufacturing processes means that much higher designations are becoming popular, all the way up to S 150s and S 180s.
What S number should I buy?
Like everything, this choice depends on your circumstances and what you can afford. A suit in the 90s to the 110s will be fine for everyday office attire. If you want something a bit finer with a more luxurious feel for a more dressy occasion, or for an all-weather suit, the 120's and 150's will supply your need. The tradeoff you make as you go up the scale is in durability, as the finer fibers are more susceptible to breakage. Super 180s fabric is so fine it can barely be seen, and very costly to boot. It also must be treated with extreme care.