These are the mounts normally used for polarisers and graduated filters which allow the filter disc to be rotated on the lens. They are supplied with the filter disc retaining ring which accommodates discs up to 2mm thickness. 3mm thick discs can be used, but there will be not residual thread to fit a lens cap or lens hood.
If the intention is to replace a damaged mount on an existing filter, please be aware that these mounts may take a different size filter disc to the one you already have. If you send us the existing filter, let us see if we can remount it for you.
