An adjustable loading/unloading mouth, including: a first tubular element (2), provided with a longitudinal axis (x); a second tubular element (3), provided with a longitudinal axis (y); connecting elements (4, 5, 6) between the first and the second tubular element (2, 3) which connecting elements (4, 5, 6) define a spherical surface (S), provided with a center (O), and which enable the first and the second tubular element (2, 3) to rotate with respect to one another about the center (O); wherein the connecting elements (4, 5, 6) include at least a first connecting element (4) and at least a second connecting element (5) which are reciprocally connectable at a joining plane (P) passing through the center (O) of the spherical surface (S) on which the first connecting element (4) and the second connecting element (5) can rotate with respect to one another about the center (O).