Abstract: A pleated-side bag or sack of flexible weldable material with a closed bottom end and a top end provided with an internal reclosing device has side pleats inserted V-wise between two bag walls forming a front wall of the bag and a back wall of the bag. The pleats extend from a bottom end to a top end. A reclosing device is formed by two pressure sealing strips below the top end. The two pressure sealing strips are formed by two hook-and-loop strips of weldable material which are fastened in parallel alignment opposite one another on the two bag walls, occupying substantially an entire interior bag width, and the side pleats project with their two V-panels between the hook-and-loop strips into the bag interior.