This is a clip-type CPL filter for smartphones. The clip is made of resin and the texture is cheap. Since it's a K&F CONCEPT, I expected it to be made of aluminum, but it's a bit disappointing. General single-lens and mirrorless camera filters can be attached, so if you buy a 67mm diameter camera filter, you can set any filter to your smartphone. However, I feel that 67mm is excessively large for smartphones, so if you already have a 67mm diameter camera lens, it may be better if you share it with a camera, but if you use it exclusively for smartphones, the 58mm diameter may be better. The CPL filter works without any particular unevenness. This is a filter that suppresses reflection, and can be used in a variety of ways, such as disappearing from a window in a night view from an observatory, etc., suppressing reflection on the surface of the water to understand the state of the water, and making the color of the sky and green vivid by removing diffuse reflections of particles in the air. After setting, the filter rotates, so it's a form of shooting by rotating it to a point where the effect is higher. It's called polarized light, and it has the effect of limiting the “direction” light enters. Also, photos taken using filters and photos taken without filters are attached for reference. Please note that the polarization tester came with another product and is not included with this product. We hope it helps you with your shopping.