LEE Filters FHFK Foundation Kit - Filter Holder (FHFK). The Foundation Kit is fundamental to the LEE Filters system. It takes standard 100mm filters, and can be constructed to take up to three filters at any one time (remember, though, the more filter guides added, the higher the likelihood of vignetting with wideangle lenses). The Foundation Kit, like all others, clips onto the adapter ring which, in turn, screws onto your camera’s lens.