The 77mm Circular Polarizer Filter (Single Coated) represents an innovative design in lens coating. Single coating is applied to one layer on each glass surface. This improves light transmission from about 92% (in uncoated glass) to about 98%. Single coating also has certain anti-reflective properties that help prevent against ghosting and internal flaring.
If you're out walking on a lovely day - in the mountains or at the beach - and you want to get a fabulous shot of a cloud-filled sky or make the water seem more saturated, then a polarizer is the way to go. This filter is the best way to make the clouds stand out, increase or decrease the saturation of the ocean or increase or decrease the reflection off the water. You can also use this filter when shooting into glass or windows since it will, again, either increase or decrease reflections.