DRAWING FRAME UNIT

A drafting system unit for a drafting system of a spinning machine having a first top roller and a second top roller spaced apart therefrom, characterized in that an apron cage to which negative pressure can be applied is arranged between the first top roller and the second top roller for guiding an air-permeable apron in circulation jointly around the apron cage and an apron top roller, the apron top roller being formed by the first top roller or by a third top roller that is assigned to the apron cage and arranged on the same side as the first and second top roller in relation to the fiber band being transported. The apron cage has at least one through-opening, to which negative pressure can be applied, for applying suction air to the fiber band running between the first and second top roller, through the air-permeable apron.