The poly filter set isn't a graduated filter. They are neutral density and they are 4x4 and come in a kit that you can attach the filter to the front of a lens. I am not sure if they work with the holder, you need to do some investigation. It doesn't appear to be what you want.

If you want a circular polarizer you go with the 105. The other square polarizers will only be linear. But good luck with finding that, I was going to buy a 105 but no one has the holder that attaches it to the lee holder.