Kodak 4x4" (100mm) 81A Color Conversion Wratten 2 Optical Gel Filter - The 81 Series of filters controls the bluish coloration that can affect daylight film. They warm scenes shot on cloudy days. They can also remove excessive blue from the effects of electronic flash.
These filters are also good for general scenics when the photographer wishes to remove the bluish cast from open shade or just add warmth to the photograph.
Kodak gelatin filters are available in 3 x 3" (75 x 75mm), 4 x 4" (100 x 100mm), 6 x 6" (150 x 150mm) and 14 x 18" (350 x 450mm).