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 and 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, and should be used when vignetting is encountered with a standard adaptor ring.