The toroidal mirrors from Optical Surfaces are focusing devices that have two different radii whose axes are oriented at 90° to each other. Toroids offer advantages where a beam must be focused and folded. Rather than using both a spherical mirror and a plane mirror for this purpose, both functions may be combined in one element. The lower number of optical elements increases energy throughput, saves money and also allows for more compact designs. Toroidal mirrors also correct for the astigmatism that result when a spherical mirror is used off axis.