I purchased this filter for use on the Mamiya 7 lenses with a 58mm fitting, and for the Canon 50mm f1.4 & 100mm f2.8 Macro lenses.
On the Canons, it works much like any other Polarizer, but image quality reminds me in some ways of the B+W/Heliopan Kaesemann Polarizers. In other words, fantastic results!
However, my main reason for choosing it was the added benefit of a numbered front ring; absolutely essential for Range-finder cameras like the Mamiya 7.
It does the job perfectly.
Tremendous value for money at the current price.