Abstract: A fuel cell stack or an electrolysis cell stack comprises a plurality of cells, which need to be compressed to ensure and maintain internal contact. To achieve an evenly distributed compression force throughout the electrochemically active area a frame with a central aperture is positioned on top of the cell stack between a resilient plate and a top plate. The enclosed aperture forms a compression chamber which is provided with pressurised gas from the cathode inlet, whereby an evenly distributed force is applied to the electrochemically area of the cell stack by the resilient plate.