Lens Accuracy: The parabolic surface accuracy PV is guaranteed to be better than 1/10 of the wavelength of light. The mirror blank is made of K9 material, some of which are high borosilicate material. The thickness of the lens is 1/8-1/10 of the diameter. The best precision main lens, aluminized film and silica protective film, the coating can be used for 8-11 years under the condition of moisture-proof storage.