In addition, it follows from the data presented in the previous section, that in URFR's with corner reflectors containing spherical mirrors, the degree of astigmatism of the beams and the ellipticity of the cross sections (for a circular aperture stop) also decreases as the resonator losses decrease. Finally, an extremely important argument in favor of using URFR's in the case of low active medium gains is the possibility of building lasers with compact exit aperture profiles. The main advantages of these lasers were discussed in some detail in Ref. 2. At this point, we merely note that with compact extraction, another factor which reduces the influence of the aberrations, is observed. As the overall cross-sectional dimensions of the part of the beam extracted from the resonator are decreased, the "geometric" divergence of the radiation generally also decreases.