Adaptor rings fit into the lens to accommodate the filter holder. Once the adaptor is in place the filter holder clips firmly to it using a smooth, quick-release, spring loaded mechanism. Sturdily constructed with an aluminium screw thread, the adaptorsScrews permanently into the front of a standard filter holder enabling a 105mm Rotating Polariser to be fitted (not included). Allows the polariser to be rotated independently of any other filters.