K&F 49MM NANO VARIABLE ND FILTER (KF01.1467)

ND-------Extend exposure time. Try an ND or neutral density filter. ND filters reduce the amount of light entering the lens. This makes it easier to achieve effects such as a shallower depth of field or blurred motion.
The neutral density filter can be adjusted from 1 to 5 stops, easy to create different light reduction effects by rotating the ring.
The front diameter is larger than the back diameter of this filter, which is specially designed to avoid vignetting at a wide-angle lens.
Allows the use of slow shutter speeds, with high-speed films or digital cameras, to record movement/image blur in subjects.