For the 100mm system.
The adaptor ring is crucial to the LEE Filters system. It screws onto the camera’s lens and, in turn, the filter holder clips onto the adaptor ring.
The wideangle adaptor ring is suitable for use with wideangle lenses. It differs from the standard adaptor ring by sitting closer to the front element of the camera’s lens. As a result, the likelihood of vignetting is dramatically reduced.