The elements corresponding to the cobalt elements makes it powerless to absorb blue light (that is, it reflects or transmits blue light, and for yellow light with different blue wavelengths, cobalt elements can completely absorb). Blue cobalt has cobalt , so cobalt can yellow light. Features - Size: 5.00X5.00X0.50cm/1.97X1.97X0.20in - Material: . - Blue cobalt is a special kind of fire-watching , which is mainly used for fire-viewing by the potassium flame reaction in chemical laboratories. - It is also used in many places in the industry (such as: cement plants, steel plants, industrial kilns). - Lightweight and portable, it is very convenient for you to carry. - The perfect workmanship will give you an excellent use experience. - Fine workmanship and creative appearance ensure its popularity and practicality. Package list: 2 x glass sheets