SmallRig Attachable CPL Filter Kit with M-mount Filter Adapter (52mm) 4388 is a filter kit, including a CPL and a M-mount filter adapter. The CPL can eliminate reflection from non-metallic surfaces (such as lakes, windows, waterfalls, glass, buildings, etc.) and thereby improve image saturation. Increased colour saturation means a bluer sky and more transparent water. It can also be used as an ND filter, reducing light by 1-2 stops. To eliminate reflection, you just need to rotate the CPL filter properly.Made of German Schott B270i HD glass, the filter features waterproof, stain-resistant, mildewproof, and scratch-resistant AR coatings, with less colour cast, as well as a CNC-machined ultra-thin frame. No vignetting even in shooting using an ultra-wide angle lens. It can be magnetically and securely attached to SmallRig magnetic filter adapter ring.