The investigation of the magnetization reversal has been performed in Fe-rich sub-micrometric glass covered wires of different radiuses. The surface magnetization reversal has been studied using the magneto-optical Kerr effect. The axial tensile stress and torsion stress have been applied during the experiments. Surface hysteresis loop was found to be rectangular because of magnetic bistability. This confirms the existence of the Surface Large Barkhausen Jump in sub-micrometric glass covered wires explained by the magnetization reversal in a large single surface domain. The analysis of the tensile and torsion stresses' transformation of surface hysteresis loop proves that magnetic bistability earlier observed in thicker glass covered microwires exists down to one order decrease of wire's diameter. (C) 2013 Elsevier B.V. All rights reserved.