Amazon.com : 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 (Nano-X Series) : Electronics
Tiffen 52mm Variable ND Filter – Pictureline
Amazon.com : NEEWER 52mm ND Lens Filter Kit: ND2 ND4 ND8 ND16, Lens Pen, Filter Pouch Neutral Density Filter and Accessory Kit Compatible with Canon Nikon Sony Panasonic DSLR Cameras with 52mm