The 19-20 inch VizoBlueX Anti-Blue Light Monitor Screen Protector Panel has been developed for people who spend many hours in front of their PC monitors. The blue light screen protector has several coatings’ layers that ensure blue light reduction, anti-flicker, scratch and crack resistance. The VizoBlueX blue light filter preserves the clear picture of your PC monitor as it doesn’t change any colors of the picture. Blue light is found in all products which use LED light such as PCs, Cell Phones, Tablets, Game machines and TVs. Blue light possesses the most energy among all types of visible light. Therefore, when blue light reaches the retina it causes many eye problems. Prolonged exposure to blue light leads to dry eyes, eye strain and fatigue. It can even cause serious eye diseases such as cataract, macular degeneration and myopia. Blue light may also trigger skin diseases and reduce your work productivity. Numerous studies have confirmed blue light reduces the hormone melatonin which in its turn deteriorates your sleeping quality. This makes you more vulnerable to depression as well. By changing your melatonin levels and sleep patterns, blue light can also impact on hunger hormones, thus increasing the risk of obesity. This computer screen protector is tested to eliminate 100% of the UV light; up to 99.6% of the most harmful High Energy Blue light (380 to 420nm) and 60% from the entire HRV spectrum between 380nm~480nm. DOES NOT work with touchscreens. Dry erase markers can be used on the monitor screen protector. The blue light blocking screen protector covers the frame and is larger than the screen. Please measure the diagonal of your screen (without the frame) or look at your screen manufacture diagonal size in inches. Although, 100% transparent and clear, due to the filters in the lens the VizoBlueX monitor screen protector for eyes may be tinted and requires that the user increases the screen brightness by up to 15%. NOT for laptops - only for monitors.