A good quality filter, made of German SCHOTT glass and installed in a sturdy, lightweight metal ring.

The ND - Neutral Density - filter of K&F concept is made of an excellent German glass to which a multi-layer NANO coating has been applied (18 layers according to the manufacturer) which allows a light transmittance of 12.5% and a reflectivity of 1.5%.
The glass also has an anti-scratch and waterproof coating, which makes it ideal even in poor weather conditions.

The neutral density colour shade is well applied on the filter and presents a light and well balanced transition.

The outer ring is CNC machined. The feeling of grip is high and the rotation of the ring is smooth; the latter is especially comfortable when positioning the filter during shooting.

The neutrality of the filter is high and the images taken, even at long exposures, do not show dominant colours.

I have purchased the 58mm diameter version but there are various sizes on the market to adapt to your lenses.

The cost of the filter is €39.99 as of May 2021. Maybe a bit high for the diameter I have but the quality of the glass is good.

I am including some photos of the product. I hope you find my review useful for a possible future purchase. Until the next review!