Polarising filters are magical things. They can reduce reflections from non metallic surfaces with merely a twist of the ring!
Another use of polarising filters is to enhance colour saturation. Have you ever seen a photograph with the deepest blue sky you've ever seen and wondered how the photographer did it? Have you ever looked at your own pale blue, wishy washy skies and thought how on earth do I do this!?!? Look no further.
By turning the ring on a circular polariser you can adjust the amount of the effect it will create. They work best when the lens is pointed at 90 degrees to the sun, in other words the sun is on your left or right, not in front or behind. They are useful wherever you want deeper colour saturation too such as on foliage. A polariser can cut out the reflection of the white sky on glossy leaves and foliage for landscape shots.
Anyway, this Hoya polariser is well made and does all of the above. It's not the slimmest so you may need to look elsewhere for a special slim version if you're using on a super wide angle lens to avoid cropping image corners.
For everyone else this is a versatile and handy addition to your kit at a very good price.