I'm really digging these new filters that K&F are releasing. The magnetic filter system is a great idea for strong ND filters because I often need to compose my shot without the ND filter attached (because it's much easier to see through the lens without it) and then attach it to take the shot; being able to simply snap the filter on to the front of the lens takes a lot of the hassle out of detaching and reattaching the filter.

The optical quality is superb, with excellent clarity and barely any color cast. The build quality of the metal rings is solid; they are smoothly machined with smooth edges and nice knurling. The rotating ND filter turns smoothly, with hard stops at either end of the spectrum so you know when you've reached the limits.

The magnetic attachment holds the filter in place snugly but it's probably best used in controlled tripod setups where you know the lens won't be bumped; I definitely wouldn't use this in any kind of crowd situation where someone or something could knock the filter off, because it wouldn't take much of a bump to cause this to happen.

There's no lens cap included, presumably because the extra weight of it would make the filter too heavy for the magnets to comfortably hold. K&F does make a magnetic lens cap, which I got with a different K&F filter set, but it doesn't fit on the outside of the ND filter because the outer ring is larger than 77mm. However, the magnetic lens cap DOES fit on the inner ring so you could use it when you're not using the ND filter. As far as I can tell you can't buy the magnetic lens cap by itself, only bundled with other filters.

This filter is easily comparable in quality to those made by Tiffen. It's fairly priced, and I would definitely recommend it for tripod-based landscape photography.