Amazon and authorized dealers via Amazon are discounting the Canon Drop-In Clear Filter A (for EF-EOS R drop-in adapters).
Authorized dealer “Neptune Photo” has it for $100.80, and Amazon (an authorized Canon Dealer) is listing it for $109.45. Compare with a regular price of $130 seen at other dealers.
This clear drop-in filter allows you to stop using an ND or CP mount adapter (without having to switch adapters). It’s not enough to just take the ND or CP filter out, as doing so can affect your ability to focus for lenses at certain distances.
Great price on the Canon filter though the Kolari Vision clear drop-in is still ~$20usd cheaper.