Good filter with small weaknesses, but rate Top

I have the Haida Slim Graufilter bought ND1000 (ND3) both in 67mm, as well as in 77mm diameter, because I did not want to spend every 100 or more euros for a filter. I tested the filter with a Nikon D7000 and different lenses.
The fact that these filters, a lens cap here is interested me relatively little, because I do not need. What am much more interested in is the quality of workmanship and the optical performance of the filter.
At the processing there is nothing to complain about. My two filters can be very good screw in the lens mount, without tilting or the like. Criticism that the scope of the filter would not be around so I can not confirm.
Most importantly, the glass and how it behaves optically. It prolongs the exposure time to 10 f-stops reliably, and uniformly over the entire surface. There are no variations in brightness between different parts of the image. The resolution and sharpness do not suffer from the filter. It is clear that there is a slight shift in color at such a strong filter. This is no different in the more expensive filters. When shooting in RAW format, however, this fact is not a problem, because you can adjust the white balance afterwards.
Only, it will increase the Flare and ghosting-susceptibility. But this is clear, because the filter is not remunerated quality. For the price this is not to be expected and therefore no reason for me to deduct a star.

All in all I can highly recommend the filter, because it is the value for money unbeatable.