Only Mystery Electronics Backboxes ensure full compatibility with our products. Backboxes conform to NEMA® standards and are UL Listed. Alignment labels aid proper installation. Trade-size knockouts for conduit system connections are included. Appropriate mounting holes are pre-punched and tapped for easy trim-out. Backboxes are required in concrete or masonry and when conduit systems are used. They are also recommended for raised wooden floor or hollow wall construction, though site conditions may make them optional.