For whole-house customization, should the back panel be 5mm or 9mm?

For wardrobes fixed against the wall, a standard 5mm back panel is sufficient; for freestanding cabinets, tall cabinets, and bookcases not against the wall, a 9mm back panel is recommended so the cabinet body is less prone to deformation. We give recommendations based on the cabinet body structure and do not uniformly downgrade to thin back panels to save costs.