Ikan Nano IR ND 2.1 6.6x6.6 NiSi Nano Infrared Neutral Density 2.1 Filter - 6.6 x 6.6 (Black) 7 Stop Infrared Neutral Density Filter 4 mm thick optical glass with precision cut, grinding, and polishing Ultra low color shifting with anti-reflective coating Water proof, scratch, and oil resistant Optimized for shooting raw 6K digital images