This is a good adjustable neutral density filter with no problems I can see. It uses K&F's special coatings to help repel dust, water and fingerprints. This filter has a magnetic attachment system, there is a magnetic ring (with no glass in it) you screw onto your lens. Then whenever you want to use the ND filter you just pop it on and pull it off magnetically, making it easy to change. The system seems to work well, but it's the only one of their filters I have which features it. By rotating the filter you can go from ND2 to ND32, or 1-5 stops.

A lot of people wonder what this kind of filter is for, basically it lets you get some different effects when you are shooting in direct sunlight. For example, you can open the F-Stop of your lens all the way to get a shallow depth of field effect, then use the ND filter to darken the image back down so it is exposed right. Another common use is so you can shoot with longer shutter speeds in bright light. This will allow you to get that effect where moving water has a soft motion blur on it by setting a longer shutter speed and adjusting the exposure with the filter. It's also very handy for shooting video in bright light. Using a high F-stop and shutter speed for this can give you a video that has no motion blur and appears to stutter when the camera pans. The ND filter can allow you to shoot with longer exposures which will give motion blur and a smoother more cinematic look when panning.

So overall a very useful filter to have if you do videos or photos outdoors in bright sunlight.