K&F Concept 72mm Nano-X HD Variable ND2-32 Fader KF01.1133 B&H
Walking Way Adjustable ND2-400 HD Variable ND Neutral Density Filter
Fader Variable ND Filter Adjustable ND2 to ND400 Neutral Density for Camera Lens Adjustable ND2 To ND400 Neutral Density Fader Variable ND Filter Camera Lens 52mm - Walmart.com
EveryMarket
FOTGA Slim Fader 82mm Variable ND Filter Review
Fader Filters vs Traditional ND Filters « Vincent Laforet's Blog