And the H/D one matches your truck, so you won't have to paint it.
I made the inner filter out of that blue synthetic air filter material. Just cut it out in circles the size of the original metallic filter that was in the separator. I tested it before I used it to see if it might melt, and it didn't. It's very porous, allowing the oil vapor to condense on the fibers and drop off. It's about 3/8" thick, and I used several layers.
You could use many other materials in place of it; it's what I had on hand. It just looked like the metallic filter might clog up easily.