Hoya Pro1 Digital CIR-PL Filter
67 mm, Polarizing filter
Hoya Pro1 Digital CIR-PL Filter
67 mm, Polarizing filter
But if you meant variable density, that would be an ND filter that consists of two polarising filters, where the upper one can be rotated in relation to the lower one and thus change the filter density. For example, this product: Hoya 77.0 Variable Density Filter (77mm, grey filter)