Amazon.com : NiSi 100X100mm Square Neutral Density Filter,IR ND64(1.8), ND 6 Stops 100mm System Optical Glass for 52mm,55mm,58mm,62mm,67mm,72mm,77mm,82mm Lens,Compatible with Lee Cokin Hitech Singh-Ray : Electronics
Amazon.com : NiSi IR ND1000(3.0) 10-Stop 100 x 100mm Neutral Density Filter, Black (IR ND1000 3.0 100x100) : Electronics