The present paper considers a ring confocal resonator in which the fulfillment of the confocal condition and the spectrum degeneracy are achieved through the use of a concave toroidal reflective surface with specified values of curvature radii in two main meridional sections. Such resonators can be used, in particular, as sensors in resonator micro-optic gyroscopes resonant optical gyroscope. This work is devoted to a review of technologies suitable for manufacturing of ring confocal resonators, and to an estimation of the deviations of the geometric parameters of confocal resonators acceptable during this manufacturing. To achieve this, the Fox and Li method is used, which was earlier modernized to calculate ring resonators with astigmatic reflecting elements.