Abstract: The present invention provides a filling sleeve which allows containers with a rectangular or square cross-section, especially bags with deep side folds, to be filled advantageously in that they are given a stable shape. The objective is achieved by means of a filling sleeve which is characterized in that, in the exit cross-section, a central region is provided with inserts and four separate exit apertures are kept open in the corners of the square or rectangular cross-section. In this way, the filling material flowing through the substantially completely open and normally undivided entrance cross-section of the filling sleeve is divided into four individual streams which are associated with the corners of the exit cross-section. Thus, while being filled, the bags are initially stabilized from the corners, as a result of which a certain tension remains in the walls between the corners, so that the walls cannot bulge out when the level of the filling material rises.