The Canon Mount Adapter EF-EOS R is a structural and electronic bridge that allows you to attach older Canon EF and EF-S lenses (designed for Canon DSLRs) onto newer EOS R-series mirrorless camera bodies (like the EOS R7, R10, R5, or R6).
Because mirrorless cameras lack an internal mirror, the distance between the lens mount and the sensor is much shorter than on a DSLR. This adapter physically bridges that gap while maintaining full electronic communication between the lens and the camera.