Color Grad® Neutral Density .6 Filter - 46CGND6 – The Tiffen Company
4x5.65 ND Filters - Pro HD Rentals
Tokina Cinema Firecrest Ultra 6.6x6.6 Neutral Density Graduated Filter
Lee 210 0.6ND Neutral Density | Hollywood Expendables
Amazon.com : Polaroid ND 0.6 Neutral Density Filter 0.6 Filter for DSLR Camera (0.6 mm Neutral Density Camera Filter, Pack of 1) (S) : Camera Lens Neutral Density Filters : Electronics