I've extensively tested this "K&F Concept Nano-X PRO Series Polarizing Filter" with my two 67mm Sony lenses (85mm + 24mm focal length) and would like to share my experience today: The packaging of the filter is impressive, as K&F has packaged this "Pro" filter very attractively and with high quality. The package includes a leather case with soft lining for storing the filter. A cleaning cloth is also included. The case has a magnetic closure and is very well made all around. The filter itself is also very well made; it has a brass frame and screws perfectly onto my two lenses. Rotating the filter to adjust it also works well. Thanks to its slim design, the filter doesn't add too much bulk to the lens. The surface of the polarizing filter has been treated with a 36-layer nano-coating on both sides, making it waterproof, dirt-resistant, and scratch-resistant. The coating makes the filter robust, and I expect it to be durable and allow me to use it for a long time. I'm also completely satisfied with the filter's properties; it reduces reflections (e.g., in water) by eliminating polarization by about 99%, and it also increases image contrast (clearly noticeable in photos of the sky/clouds). I've already used the filter to photograph landscapes, and I'm very satisfied with the image quality. I haven't noticed any optical impairments when using the filter. I can highly recommend the "K&F Concept Nano-X PRO Series Polarizing Filter."