What does the "V" and "R" stand for in OutBack Power's VFXR inverter/chargers? Posted by Frank Molina on Feb 19th 2021 “R” indicates that the FXR was designed for renewable applications. Off-grid and grid-interactive functions are integrated in the same inverter. Vented models are preceded with “V”, as in “VFXR3648A FXR OutBack Power FX OutBack Power inverter