This RibMount™ System Electrical Outlet Box mounting base is custom made specifically for buildings with metal rib siding (AG-Panel) to assist with mounting interior electrical outlet boxes. The RibMount™ System Electrical Outlet mounting base allows the outlet box to be installed exactly where desired regardless of metal rib location. Material is PVC (paintable) and resists yellowing over time due to UV protection added. Actual dimensions are 7.25" x 7.25" x 1.5" with 2.25" wide x 3.63" tall rectangle cutout. IMPORTANT: Select routed offset distance from center in dropdown menu ("X" dimension in drawing). All electrical components should be installed by a qualified professional.