Hollow fibres have single or multiple holes, a normal crimp and are supplied “dry” or with a silicone layer. HCS stands for Hollow Conjugated Siliconized. These fibres are actually made from two different polyester polymers and are therefore bi-component. This chemical property and a special production process gives them a 3D crimp to provide a higher puff. Hollow fibres are generally used for high volume applications, to improve thermal and acoustic insulation and, for example, to improve the moisture wicking properties in beds and upholstery. We also stock hollow fibres with a dtex of just 1.6 or 10 holes for special-purpose requirements.