All of the colour lenses are German Din standard and filter out harmful ultraviolet and infrared wavelengths, to provide full protection for your eyes.  
The number denotes the amount of shade provided by each lens, number bigger, more darker, you should select the one that is most comfortable yet provide clear visibility.
Perfect for welding shade lens replacement, also can be used for dark film filter.
Size: 105mmLx83mmWx3mmD 

Darkness option: D9,D10,D11,D12