Amazon.com : NEEWER 77mm Variable ND Filter ND2-ND400 with Putter, Adjustable Neutral Density Camera Lens Filter(0.3-2.7, 1-9 Stops), 30 Layer Nano Coated/HD Optical Glass/Water Repellent/Anti Scratch/Ultra Slim : Electronics
Amazon.com : K&F Concept 55mm Variable ND2-ND400 ND Lens Filter (1-9 Stops) for Camera Lens, Adjustable Neutral Density Filter with Microfiber Cleaning Cloth (B-Series) : Electronics
Gear Review: 4 New K&F Concept Filters Put to the Test
Ultimaxx 58mm ND2 to ND400 Slim Fader Variable Adjustable ND Neutral Density Filter for All DSLR Camera Lens with Same Filter Thread Size - Walmart.com
K&f Concept Nd2 To Nd400 Nd Lens Filter Slim Fader Variable Adjustable Neutral Density 49mm 52mm 58mm 62mm 67mm 77mm - Camera Filters - AliExpress