It converts daylight-balanced light to tungsten (3400K) while simultaneously reducing light by 1 stop (ND 0.3) to help control exposure.
Yes, it fits any standard 4x5.65-inch (Panavision size) matte box tray, including professional models from Arri, Tilta, and Bright Tangerine.
Using a single combination filter reduces the risk of 'ghosting' and flare caused by light bouncing between multiple layers of glass.