Pressed bends are designed for building ventilation systems based on spiral and plain ducts. Seam welds provide air tightness class D without the need to use any other sealants. In ventilation and heat recuperation systems, the double EPDM gasket provides air tightness class D according to EN 12237. The piece is connected with a duct by inserting one into the other. The pressed form of the ventilation piece helps to reduce the flow resistance and the pressure loss.