Canon - C-PL Drop-In Filter Mount Adapter EF-EOS Rhttps://www.photocineshop.com/en/products/CANON-Drop-In-Filter-C-PL-Mount-Adapter-EF-EOS-R-74LH9H?cat=764
Drop-In Filter Mount Adapter EF-EOS R takes the functionality of Mount Adapter EF-EOS R and adds the ability to use drop-in filters, removing the need to fit filters on the front of a lens, especially useful for wide-angles with a large front lens element. It’s available with either a variable neutral density (V-ND) filter or circular polarising (C-PL) filter, and a clear (CL) filter is also available for shooting without filter effects.
Polarising filters cut through glare and haze and reduce the amount of light reflecting from glass surfaces. The filters also boost colour saturation and help add impact to colourful scenes.