Assemblies or MEA devices (Membrane Electrode Assembly) comprising a membrane and two electrocatalytic layers on each side thereof, wherein:the area of each of the two electrocatalytic layers is lower than that of the membrane;on each of the two sides of the ionomeric membrane there is at least one subgasket, applied on the MEA non catalyzed area;the edges of the ionomeric membranes being enclosed among said subgaskets.