I'm very happy with my purchase of the K&F 1-5 stop ND filter. I recently purchased and then returned the Neewer ND 2-400 filter for $26. I thought it might not be of the best build quality but I never expected the pictures shot through the filter to be so blurry. I bought it to shoot portraits and the resulting photos where completely unusable. Everything I've shot with my new K&F filter has been usably clear. It cost more than twice as much but still didn't break the bank.

The pictures I've included with this review were both taken with my neewer S101-300W strobe lights.

(Photo f2.8) Head & Shoulder portrait zoomed in on Eye with Filter @ 5 stops on the K&F filter:
• f/2.8, 1/200 sec., ISO-100 shooting with a strobe light.
• Canon 77D w/Canon 70-200 f2.8 @ 80mm
(Photo f10) Head & Shoulder portrait zoomed in on Eye with no filter:
• f/10, 1/160 sec., ISO-100 shooting with a strobe light.
• Canon 77D w/Canon 70-200 f2.8 @ 115mm

The latch on the little round plastic box that came with the filter to protect it doesn't work very well. You have to push the button really hard and kind of use your fingernail to push the button to the side to get it to open. Kind of a pain but the product itself works really well and I'm very happy with it. It came super clean with no smudges or finger prints on the glass.