Filament core spinning wraps wool or wool-blended fibres around a central continuous filament. Woolmark lists possible cores including elastane, polyester, polyamide and regenerated cellulose. The outer wool maintains the yarn's familiar appearance and handle, while the centre can contribute strength, stretch or other functional properties.

Core-Spun Wool Can Hide a Different Filament Inside the Yarn

This makes a complete composition label important during identification. A fabric that looks and feels woolly can still contain a deliberately engineered internal component. The core choice and the amount of wool coverage help explain performance without requiring the surface to resemble the filament hidden within it.