Refill unit for menstrual products, which is formed by a cardboard cut-out (10a, 10b, 10c) having the following elements which are articulated with respect to one another by folding lines: - four side walls comprising: - a first pair of opposite walls, referred to as the front face (F-av) and the rear face (F-ar), which are rectangular in shape and of equal width, wherein the length of the front face (F-av) is greater than the length of the rear face (F-ar), wherein the front face (F-av) has, at an upper end, a detachable part (Ouv), which is pre-cut to a predetermined shape, for the dispensing of the products contained in the refill unit, - a second pair of opposite walls, referred to as the first side and the second side, of equal width, - an automatically locking base, referred to as the auto-lock bottom, each element ( F1, F2, F3, F4) of which is articulated by a respective folding line ( P1, P2, P3, P4) at a lower end of each of the four side walls, - a first flap and a second flap, each connected in an articulated manner by a respective folding line ( P5, P6) as an extension of the upper end of the front and rear faces, wherein the first flap ( R 1) is connected in an articulated manner by a folding line to the pre-cut detachable part ( Ouv) of the front face ( F-a v), - a first closing section and a second closing section, each connected in an articulated manner by a respective folding line ( P7, P8) as an extension of the upper end of the first and second sides ( C1, C2), wherein the first closing section (V 1) has a tongue and the second closing section has a locking slot ( Fv), wherein the first and second closing sections ( V1, V2) cooperate with each other by the insertion of the tongue into the locking slot ( Fv) in order to ensure a reversible locked closure of the refill unit, at the opposite end with respect to the auto-lock bottom. - four side walls comprising: - a first pair of opposite walls, referred to as the front face (F-av) and the rear face (F-ar), which are rectangular in shape and of equal width, wherein the length of the front face (F-av) is greater than the length of the rear face (F-ar), wherein the front face (F-av) has, at an upper end, a detachable part (Ouv), which is pre-cut to a predetermined shape, for the dispensing of the products contained in the refill unit, - a second pair of opposite walls, referred to as the first side and the second side, of equal width, - a first pair of opposite walls, referred to as the front face (F-av) and the rear face (F-ar), which are rectangular in shape and of equal width, wherein the length of the front face (F-av) is greater than the length of the rear face (F-ar), wherein the front face (F-av) has, at an upper end, a detachable part (Ouv), which is pre-cut to a predetermined shape, for the dispensing of the products contained in the refill unit, - a second pair of opposite walls, referred to as the first side and the second side, of equal width, - an automatically locking base, referred to as the auto-lock bottom, each element ( F1, F2, F3, F4) of which is articulated by a respective folding line ( P1, P2, P3, P4) at a lower end of each of the four side walls, - a first flap and a second flap, each connected in an articulated manner by a respective folding line ( P5, P6) as an extension of the upper end of the front and rear faces, wherein the first flap ( R 1) is connected in an articulated manner by a folding line to the pre-cut detachable part ( Ouv) of the front face ( F-a v), - a first closing section and a second closing section, each connected in an articulated manner by a respective folding line ( P7, P8) as an extension of the upper end of the first and second sides ( C1, C2), wherein the first closing section (V 1) has a tongue and the second closing section has a locking slot ( Fv),