R-Panel vs. PBR Panels: What’s the difference? R-Panel and PBR Panels look very similar, but have different applications- so what’s the difference? The difference lies in a small “leg” called a Purlin Bearing Ribs, or PBR.  This leg adds strength to PBR panels that enables the panel to be used in both siding and roofing applications.  R-Panels, on the other hand, do not feature this leg and are used only…