The Drop-In Circular Polarizer for EF to RF Mount Adapter from Meike adds a rotating circular polarizing filter to the MK-EFTR-C lens adapter, which allows Canon EOS-EF type DSLR lenses to be mounted onto Canon EOS-RF mount mirrorless camera bodies. This filter also fits the Canon EOS-EF to EOS-RF lens adapter, and fits in place of the drop-in filter holder that comes with the lens adapter. Since this filter is positioned between the rear of the lens and the camera body, it can be used with any lens, even lenses without standard filter threads. This adapter features a geared thumbwheel to rotate the filter into the desired position for polarization.

A circular polarizer helps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a nonmetallic surface. A polarizing filter arranges and filters directionally polarized light perpendicularly to the reflected light, resulting in a noticeable reduction of glare and reflections from nonmetallic surfaces and an increase in the saturation of skies and foliage.