Freewell 52 mm base ring with lid for Real Locking VNDFreewell 52 mm base ring with lid for Real Locking VND The Freewell 52mm base ring is an indispensable part of the Real Locking VND CPL system, which allows you to securely and quickly mount filters to your lens. Made of precision milled aluminum, it provides a solid mount and compatibility with the rest of the system from VND filters to caps. The 52mm model fits lenses with such a thread and allows the system to be extended to smaller diameters.