A type of component fibre described as multiple-interface or filament-in-matrix. The "island" are fibrils of one or more polymers imbedded in the "sea" (or matrix) consisting of another polymer. The matrix is often dissolved away to leave filaments of very low denier per filament. These fibres have been used in ion-exchange products and in imitation fur products as well as to produce textile products with a different hand.