[Glass] I decided on a circular filter, due to the ease and speed of assembly, I also found in the Haida brand an excellent quality glass, a very high control of certain color dominances, compared to much more expensive filters.
I wanted to buy polar pro, but the cost is high compared to this one, and although there are differences, it is not something that makes me consider investing so much money in a glass that will not be put every day in my lenses. As a bonus, I have taken the Haida to very extreme tests in the Chilean heathen, in the cold and in the Atacama desert, in the heat and dust.
I recommend it

[Glass] Great filter at a reasonable price.

[0.18 lb] I have tested this filter three times now in daylight and artificial light and am very satisfied; it's earned a place in my kit. Density was perhaps a quarter stop less than 10 stops. The color is extremely accurate, varying from my no filter control shot by about 50 degrees K cooler and (in Capture One) 2.5 greener. These are extremely small adjustments. My 10 stop B+W gives a very strong red-warm cast that is hard to eliminate completely with a grey balance, a color cross-over likely due to infrared leaking through the filter. Sharpness: using a Nikon D850, 20mm f/1.8 lens, tripod, mirror up, electronic front curtain shutter, f/8, default settings in C1, at 100% view onscreen the Haida is indistinguishable in the center from No Filter, and at the edges shows only a tiny resolution loss (typical of any filter). You have to go to 200% and compare side by side to see the subtle differences. With a longer focal length lens, I expect any differences to be even smaller. My verdict: excellent filter at a good price. I plan to buy a second in a different size and see no reason to search other brands.

[Glass] Works as expected, but keep in mind most neutral density filters have some color cast.

[0.18 lb] I've been using my new Hasselblad X1D II for about six months, and needed to improve the prospects of sky effects, as Scott Kelby discusses in his classes. This filter provides that capability for the XCD lenses

[Glass] Inexpensive. Dead-on 10 stops (based on some fairly limited testing). Throws a little yellow-orange-brown ish color cast, but it is fairly uniform making it manageable and correctable.

[0.18 lb] I own the Lee Filters 'Big Stopper 3.0 ND filter (10 stop) and have used it quite often. After seeing the reviews on this filter, I thought I would try it against the Lee system. This filter produces more natural and warmer colors than the Lee, the contrast seems to look a little better. Haida's M10 filter system doesn't leave a lot to be desired though but their ND filters are definitely worth the investment!!! This filter will work in the Lee holder,as it comes with a layer of foam that can be applied to keep light from bleeding past. I am very pleased with the results and would highly recommend this filter for anyone who wants to do long exposure photography.

[Glass] Crisp clean image. Had some great results first time out on a 125 second exposure right before sunset.

[0.18 lb] Purchased the 6 and 10 stop versions to pair with the Kase K9 holder. Both of these filters create superb results with no loss in sharpness and no color cast whatsoever. Made the switch from a screw-on variable density that always caused problems under bright and side lighting conditions. These allow very accurate control of exposure to create blurred water / clouds. Easy to clean and sheds water well. Great value.

[0.18 lb] Works as expected, but keep in mind most neutral density filters have some color cast.