I have been using the K&F CONCEPT Go Ultra CPL ND filter set (pack of 4) for a few weeks now and am very satisfied. Strengths: Very good glass quality: The image quality is clear and rich in contrast, with no visible loss of sharpness or color tint. To be screwed on like a protective filter: Can be screwed onto the front of the lens and virtually replaces the permanent handle for lens protection — great for working quickly. Larger than the original lens: The front dimension is deliberately generously designed, meaning that the effect is uniform without vignetting, even at a wide angle. Sophisticated design: Clean lettering, grippy knurling, runs smoothly — you can tell that thought has been taken here. Metal thread: sturdy, perfect fit and durable; no wobbling, no snagging Good price: Absolutely fair for the quality offered and the scope of delivery. Weakness: Large plastic case: Protects well, but it's a bit bulky for my photo backpack. Practical use: ND filters in particular are indispensable for generating motion blur (flowing water, road traffic, people motion) in bright lighting situations. The CPL works reliably against reflections and ensures rich colors. Conclusion: A highly recommended set with high-quality glass, clever design and robust metal thread. Anyone who works seriously with ND/CPL gets a lot of money for their money — only the case should be more compact.