The lenses at the time of manufacture, in General optical glass formulations and then joined part of the metal oxides, such as drilling, chromium, strontium, iron, nickel, manganese and rare earth metal oxides such as neodymium and, and so on. These metal oxides can cause glass to a certain wavelength of light for selective absorption of electromagnetic waves, such as cerium and iron oxides can absorbs ultraviolet light. This glass lenses can reduce the amount of certain wavelengths through the lens, to mitigate or prevent eye damage. Protective lenses of different colours absorb different colors of light. These glasses are divided into two broad categories, one for the absorption, reflection, which is used the most.
Lens rushes are round, specifications for the diameter expressed in units of mm, φ 48, 50, 52, 56, 60, 65, 70, and so on. Most commonly used for PHI 56, 60, 653 specifications. Due to the large frame of pop, φ 70, an increase in the use of large size lenses.