The Sony a7 III / a7R III uses the same Really Right Stuff plate as the Sony a9. All plates feature the engraving for the a9 but fit both camera body styles.
RRS camera body plates are all custom designed for each camera body and precision machined from solid blocks of 6061-T6 aluminum. Fully compatible with any standard 1.5"-dovetail style quick-release system, our plates feature precisely contoured anti-twist flanges for a perfect fit that prevents twisting between the camera and our plate. All of our quick-release plates utilize a custom machined 1/4"-20 threaded, captive-style mounting screw that threads into the tripod mounting socket of your camera body.
As part of a modular system, this conventional base plate still functions as a traditional camera mounting plate, but also has the added flexibility of accepting a separate dedicated vertical L-Component to create a fully modular L-Plate with two dovetail mounting surfaces. You can purchase the dedicated vertical L-Component as a separate add-on, or as a set package with the base plate.
To install the base plate, remove the battery door from the camera body and install the battery door onto the RRS base plate. How to Use Plates with the Sony Cable Anchor
*** Please note that when choosing the "Yes, I Plan On Using The Battery Grip
" option above, a BPNS plate will be used and not a modular plate. ***