I was concerned about buying this filter because the price was very low compared to Hoya. The decision to purchase was eventually influenced by the fact that the price was an 'offer' from a higher price and other reviewers seemed happy about the optical performance (except one).
In the end, I decided I wanted to experiment with a polariser and this seemed to offer a good starting point. So what I got?
As an engineer, I think the mechanical quality is good and the thing seems to do what it says on the box. To newcomers , I would make the point that the setting of a polariser seems to be quite critical and it is easy to miss the effective part of the rotation. That brings me to my one criticismm of the design...
The filter has a little handle screwed into the side. Would you believe that the weight of the little handle can cause the filter to move off setting with very little provocation. It is difficult to find when on the camera. This makes it awkward to use compared to the excellent knurl on the filter body. A previous reviewer has complained that the handle was easily broken and not much missed.
My advice to users is... take the handle off!. It unscrews easily. Then you have a nice filter that stays put when you take your hand off it.