1 micron (µm) is equal to one thousandth of a millimeter, also equal to one millionth of a meter.

In the world of wool, the micron is the unit of measurement for fiber diameter, and it is the main point that determines the choice and end use of wool fibers by manufacturers. Wool with a low micron gauge has finer and softer wool fibers than wool with a higher micron gauge.

Merino wool is the type of wool with the lowest micron measurement and is therefore very suitable for use as the inner layer of clothing, because when the fine merino wool fibers touch the skin, they bend - unlike other coarser types of wool that sting and itch. Fibers measuring from 25 microns and up are seen as coarser and stronger, suitable for, for example, durable wool socks or seating mats. In comparison, a human hair is usually 50-100 microns.

What else are microns used for?

Microns are also often used as a technical term for the fineness (hole size) of a filter element, for example on oil filters for cars and other machines. The micron of the filter then determines the size of particles that will be able to pass through the filter.

A 20 micron filter captures particles equal to or larger than 20 microns and will allow larger particles to pass through than a 10 micron filter.