K&F Concept 52mm Variable ND Filter ND2-ND32 Camera Lens Filter (1-5 Stops) No X Cross HD Neutral Density Filter with 28 Multi-Layer Coatings Waterproof : Amazon.com.au: Electronics
Tiffen 52mm Variable ND Filter | Creative Head Rentals
Amazon.com : 52mm ND Variable Neutral Density Filter for Leica 18-56mm f/3.5-5.6 Vario-Elmar-T : Electronics