Adaptor rings fit onto the lens to accommodate the filter holder or lens shade. Once the ring is in place the holder clips into place using a smooth, quick release spring loaded mechanism. Sturdily constructed with an aluminium screw thread, the adaptors are available in both standard & wide angle configurations. Special or non standard sizes can be made to order. Wide-angle adaptor rings are designed so that the filter is placed as close as possible to the front element of the camera lens, & should be used when vignetting is encountered with a standard adaptor ring.