This K&F Concept kit is quite nice. I had not used magnetic filters before, but the concept is pretty ingenious, it's a little surprising that it took us until the last ten years or so to come up with it (okay, maybe they've been around for longer, but if they have I haven't seen them). This uses a very, very slim screw-on adapter ring, and then these equally slim filters pop on and off magnetically. It just works great.

The design is good, and I'll throw in a comment on the design of the case as well. It's thoughtfully put together with a secure zipper closure, but also has a magnetic flap, so in a pinch you could leave the zipper unzipped and the flap would keep the kit closed up as long as you're not handling it roughly. I wouldn't rely on just the flap if you're utilizing the belt/strap attachment and dangling it off a bag, belt or back. The magnet is just strong enough, but not enough to keep it together if it were to be jostled.

I kind of wish this kit came with a simple UV filter as well, because it can be a little hard to locate the right one on the K&F website. I get that this is very much a ND filter kit, but, since I have the adapter installed, why not just include a UV filter to make use of that adapter when I don't need the ND filter? Just a thought.