The K&F Concept 77mm Circular Polarizers Filter Super Slim with 36 Multi-Layer Coatings, High Definition Circular Polarizing Filter (CPL) Camera Lens Filter (Nano-X PRO Series):

Is one of the finest quality filters I've used. Everything about this is premium. From the packaging to the filter wallet to the product itself is top notch. It has a brass powder-coated frame and high quality, crystal clear optics. A filter I don't feel too bad putting in front of my best glass. The threads are precisely machined and screw in and out very smoothly. The CP rotation feels impossibly, buttery smooth. Like its hydraulic but it's not, it's just a ridiculously smooth action. Like a high quality potentiometer. The knurling feels very nice, and over all the whole thing feels really great in the hand. As far as the polarization effect it works as it should and as expected, and with crystal clear optics. The included filter wallet is made from suede and heavy denim, with a pull ribbon to retrieve the filter with out stick your fingers down the pouch. The whole thing is rather lux. The packaging itself is a very classy, thick black box, with gold accents. the box also turns into a picture frame. The package also contains a microfiber cloth. Overall this is a very deluxe filter. It is a bit pricey, however the quality meets the price for sure. You get what you pay for sometimes and this is one of those times. You don't want to buy top quality lenses, costing thousands of dollars, and put a cheap filter on it. This is the type of filter you can feel good using on your best lenses. Precision machining and great quality glass.