The 49mm standard adaptor ring from LEE is crucial to the LEE Filters system, allowing you to attach the LEE100 filter holder to your lens. The adapter ring screws on with a fluid action, thanks to the sturdy construction and aluminium screw thread. This is the non-wide angle ring adapter for the LEE100 holder, and is available in a variety of thread sizes to fit each of your lenses. Please check the thread size on the front of your lens before purchasing