Kolari Vision releases new drop-in filters for Canon EF to RF adapter and they're available now - DIY Photography
Benro Aureole detachable dual drop-in filter mount adapter for Canon RF & Sony E Mount cameras - Newsshooter
A Closer Look At the Awesome Canon EOS R Drop-In Filter Mount Adapter | Fstoppers
Drop in Filter Mount Adapter EF-EOS R | Canon Australia
Arri PL (Positive Lock) Mount Lens to Canon RF Mount Mirrorless Camera Body with Built-In Variable ND Filter – Fotodiox, Inc. USA
Amazon.com : JJC 2 Pack Light Leak-Proof Lens Filter Adapter Cap Cover for Canon EF to RF Drop-in Filter Mount Adapter EF-EOS R with Clear CPL Variable ND Filter A : Electronics
NDT Fusion Auto Adapter - Canon EF Lens to L-Mount Cameras w/ Variable ND – Fotodiox, Inc. USA
Canon EF to RF Adapters
These are the First Third-Party Drop-In Filters for Canon's EF-RF Adapter | PetaPixel
Breakthrough Photography's new EF to RF drop-in filter adapter is $100 cheaper than Canon's - DIY Photography
Breakthrough announces first third-party EF to RF Drop-In Filter Adapter: Digital Photography Review