Comprehensively illustrated with seven figures, the best demonstration of the nature of bi-component fibres is shown by figure 1 that has twelve cross-sections of the commonly used types, together with possible material mixes and other technical data. One common reason for using two materials in one fibre is to produce a self-crimping action when the two components have different shrinkage characteristics. Another is to achieve good thermal bonding properties. Figures 3 and above show equipment ranging from a complete staple fibre line for bi-components from Neumag GmbH to individual components such as a spinning beam and the hole arrangements necessary to produce side by side or core-sheath fibres. Calculations for the pressure drop of each of the two melt streams, an important operational parameter, are shown in an iterative technique that often needs just three iterations. The technology is not yet considered to be mature, and research and development continues.