Specification:

CPL Lens Filter:

• A polarizer is different than most filters in that it is composed of two pieces of glass, mounted independently inside a round frame so that one can be rotated relative to the other. 
• As it is rotated, it increasingly cuts out glare and haze. 
• With an SLR, you can actually observe this change through the viewfinder.
• Polarizers reduce glare from water, glass, or any non-metallic surface. 
• You can also use a polarizer filter to darken blue skies.