Canon EOS MX cameras are entry-level APS-C models, like the M5. Canon EOS MXX cameras are entry-level APS-C models, like the M50. The “R” is the initial letter of the first word in Canon’s development concept for the range (Reimagine Optical Excellence). The “M” stands for Mobility. The “X” is usually a number.
This item Canon EOS 6D 20.1 MP CMOS Digital SLR Camera with 3.0-Inch LCD (Body Only) Canon EOS 6D Mark II Digital SLR Camera Body – Wi-Fi Enabled Canon EOS 5D Mark III 22.3 MP Full Frame CMOS with 1080p Full-HD Video Mode Digital SLR Camera (Body)