Woolmark describes wool wadding made from layers of carded batts and filling made from small wool clusters such as nepps or noils. These forms use the fibre's crimp to hold insulating air spaces within jackets, bedding and other products. Moisture-vapour handling is another part of the comfort explanation.

Wool Fill Uses Crimped Fibres to Build Insulating Air Spaces

The thickness, mass and arrangement of the fill affect the finished insulation. A wool-filled label does not specify one universal warmth level or replace details about the cover and quilting. Understanding whether the product uses a batt or loose clusters helps explain its construction.