What is Fiber Fineness?

An S number on the label of a wool fabric shows the fineness of the wool fiber (measured in micrometers) used in apparel production.

Fiber fineness is one of the factors determining the quality and performance of a wool product and it's also an important marketing device.

The S numbers may be used on products of 100 % wool and on these of at least 45 % wool.

It is a direct and precise measurement of the thickness of the fiber.

The S number of fiber, and hence of yarn, fabric, or garments made of that fiber, is determined using the international standard promulgated by the International Wool Textile Organisation (IWTO).

The Code defines the S number by correlation to maximum fiber diameter.

For example, 80s must have maximum fiber diameter of 19.75 micrometres or finer and 90s, 19.25 micrometres or finer. This scale continues to the 210s at 13.25 micrometre or finer.

Super S - originally that sign meant the best wool, today it means pure new wool (also called virgin wool because it is not mixed with any recycled wool) and can also be used for fabrics made from wool blended with rare fiber (for example mohair, cashmere wool and alpaca) or silk.

The terms Super 100, 120, 130, 140 or 150 show the fineness of the wool thread. The higher the numbers are the better and finer the quality of the wool is.

The tightness of the wool makes it less likely to wrinkle and in this case also more expensive because it requires more wool fiber.

You can see the wool quality printed on the label inside the suit.