HOLLOW FIBRE FLEECE SOCKS Newly developed, highly functional fleece material for an optimal body climate. Power Stretch Hollow Fibre- Better insulation than regular fibre because it is hollow and filled with air. Flat-lock stitched for comfort. Hollow Fiber Fleece (90% Polyester, 10% Elastane). • Unisex: S, M, ML, L, XL, XXL