A Drop-in clearfilter for the Canon EF-EOS R Mount adapter. Canon Drop-in Clear Filter for EF-EOS R Adapter A drop-in clear filter for the EF-EOS R mount adapter. This is aimed at the individuals that do not want any filter effects but have purchased the Drop-in Filter Mount adapter, the clear filter fills the gap where you'd typically have the polariser or Variable ND filter to give you a clear image that is not distorted in any way.