Yes, the lens cover is magnetic also threaded, and the lens can be screwed on directly, or it can be magnetically attached by a magnetic attachment ring or filter, which is a two-in-one function; 

In order to buy a lens filter, you need to know the diameter of the lens. The size is usually displayed next to the ø symbol on the front of the lens. 

You need to install the magnetic attachment ring first, and attach the ND1000 filter to the magnetic attachment; 

You need to install the magnetic attachment ring first, and attach the ND1000 filter to the magnetic attachment; 

I've never used Hoya ND's, but I have GOBE, KERNEL, ZOMEI, and K&F ND filters. Out of all of them, I like the K&F the most because the colors look great out of the camera and they don't create a vignette around the edges like some of my other nd's which I hate. Because of the great out of camera colors, it gives you more to work with on post-production when you shoot on a flat profile. Also, I've used them during night photography on bulb mode to do light painting and the 4 - 6 stop ones work great for this. Overall, I think for the money the K&F filters are worth it. Awesome product!