What a micron count actually tells you

"The finest cashmere" means nothing. Here are the three numbers that mean something.

Micron is fibre diameter. Cashmere runs from about 14 to 19 microns. Finer is softer, and finer is more expensive, but finer alone is not the whole story.

Staple length is how long each fibre is. This is the number nobody quotes, and it is the one that decides pilling. Short fibres work loose from the yarn under friction, ball up, and become the pills you shave off a jumper in its second month. Grade-A cashmere is longer than 34 millimetres. Grade-C can be half that.

Ply is how many yarns are twisted together. Two-ply is the minimum for a garment you intend to keep. Single-ply is lighter and cheaper and will go through at the elbow.

We knit at 15.5 micron, 34-millimetre staple, two-ply. A jumper made this way costs about three times what a grade-C equivalent costs and lasts something like eight times as long, which is a bargain expressed inconveniently.