The “Super” number on a wool tag is a fineness rating. It refers to the diameter of the wool fibre — higher number, finer fibre. A Super 100s wool has fibres around 18.5 microns; a Super 150s is closer to 16 microns.
Finer feels softer and drapes better, but it also wears out faster. A Super 150s suit is a special-occasion garment. A Super 110s or 120s is what you want for a daily blazer.
Don’t buy the highest number. Buy the right number for the way you’ll wear it.
The mill matters too — and not because of snob value. The big Italian mills (Loro Piana, Vitale Barberis Canonico, Reda, Drago) are vertically integrated: they own the spinning, the weaving, the finishing. The cloth is consistent batch to batch. Cheaper cloth varies — same code, different drape three months later.
When we quote a suit, the mill is on the invoice. You should know what you’re wearing.