The frame is made of deciduous plywood with a characteristic structure recommended for slats carrying heavy loads. It consists of 28 birch spring slats, attached to the frame frame, in holders made of plastic resistant to cracking and deformation. Additional transverse lath connecting the frame in the central part. Transverse hardness adjustment on five slats in the lumbar region. Longitudinal tape strengthening bent strips. Recommended for all advise mattresses.