A disposable absorbent insert (50), configured for use with a reusable outer cover (20), which has an absorbent core inside an envelope-like structure formed by an upper sheet (51) and a backing sheet (52), in which the absorbent insert (50) has: an absorption capacity of the insert, measured according to the centrifugal retention capacity test； a mass of the absorbent insert； and an absorption capacity of the unit insert, defined as the ratio between the absorption capacity of the insert and the mass of the absorbent insert； characterized in that the absorbent core has a part that is free of air felt that is disposed between the upper sheet (51) and the backing sheet (52), wherein the absorbent core includes a layer formed at least partly by a substrate, absorbent particles distributed of a superabsorbent polymer or gelling absorbent material and a thermoplastic adhesive composition that captures the absorbent particles distributed and adherent to at least parts of the substrate, thereby immobilizing the absorbent particles on or near, and with respect to substrate, and the absorption capacity of the insert is at least 200 grams, the absorption capacity of the unit insert is at least 8 grams per gram, and the mass of the absorbent insert is less than 50 gramsUna pieza de inserción (50) absorbente desechable, configurada para usar con una cubierta exterior (20) reutilizable, que tiene un núcleo absorbente en el interior de una estructura parecida a un sobre formada por una lámina superior (51) y una lámina de respaldo (52), en el que la pieza de inserción (50) absorbente tiene: una capacidad de absorción de la pieza de inserción, medida según el ensayo de capacidad de retención centrífuga； una masa de la pieza de inserción absorbente； y una capacidad de absorción de la pieza de inserción unitaria, definida como la relación entre la capacidad de absorción de la pieza de inserción y la masa de la pieza de inserción absorbente； caracterizada por que el núcleo absorbent
