An adapter is named for the lens it accepts and the body it attaches to. EF-EOS R means EF lens to EOS R body, not the reverse.
Make the exact-model decision
Write the route as lens mount → adapter → camera mount and compare with the maker's diagram. Record the adapter model and read its direction as lens side to body side. Check the maker’s excluded lenses before attaching anything.
A manufacturer example
Canon describes the EF-EOS R adapter as an EF/EF-S-lens-to-EOS-R-body route. The adapter model must be identified before considering a drop-in filter or control-ring variant. Use the linked page for its stated model and revision; a different model may need a different support document.
Where to draw the line
Electronic contacts, a manual ring and a glass-containing adapter solve different problems. Avoid extrapolating from one adapter generation to another. If a source does not address the exact feature you need, record that feature as unknown rather than treating silence as support or incompatibility.
Your next step
Take the model code from the body or lens label, open the official source below, and compare its scope with the equipment you have. Then use the inspect directed adapters to organize what is known. Do not mount an item that resists or appears on a maker’s exclusion list.
Official sources and scope
Checked for this reference on October 30, 2026. Product firmware and support lists can change; inspect the current maker page for your exact revision.