The Cinema 4x5.65" True Color Rotating PL Linear Polarizing Filter from NiSi reduces reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface. A polarizing filter arranges and filters this directionally polarized light perpendicularly to the reflected light, allowing for much of this light absorption. This results in a noticeable reduction of glare and reflections from non-metallic surfaces and an increase in the saturation of skies and foliage. This True Color PL linear polarizing filter removes the warm tone seen with other brands of polarizing filters and provides an accurate, true color representation of the scene. This filter is made of optical glass, and the edge of the polarizer is sealed to keep moisture from entering the filter.
 
Designed with the cinematographer in mind, this filter is 6mm thick and fits into a standard 4 x 5.65" matte box tray. It features an M0.8 focus control gear, allowing adjustments to be made manually or with a separately available small motor attached. The aluminum frame is light, stable, and durable and includes a 1/4"-20 thread to allow the PL to be used with a magic arm. Included with this filter set is a 15mm support rod and a padded storage pouch.
 
Source: B&H
https://www.bhphotovideo.com/c/product/1711261-REG/nisi_nic4565tcrpl_cinema_45_65_true_color.html