The Swift Magnetic Filter Holder from H&Y Filters is a "C" Swift System module. It requires an "A" base module like the Swift Magnetic Variable Adapter or the Magnetic screw-in adapter for wide angle lens, plus a "B" module like the Swift Bridge Ring. A drop-in filter rack can be used to utilize a polarizing filter or a Swift magnetic VND filter. The filter holder can be used for holding up to three 100mm filters.