I’m selling my Arca compatible Really Right Stuff baseplate/ grip for Sony A9, A7iii and A7riii cameras.
I used this on my A7riii most of the time as it make the camera more comfortable to hold, especially with bigger lenses.
It is perfectly shaped for the camera and has a very rounded off design which is much more comfortable to hold than the Small Rig L bracket.
It does require that you remove the battery door but it has a gasket to maintain weather sealing.
I used it for years in all types of weather with no issues.
It also has a magnetic Allen key for installation and removal.