The Super Blue New Work Round 25 cu. in. Non-Metallic Hard-Shell Ceiling Box is designed to not break or crack, even in extreme conditions. Box is mounted on adjustable 11-1/2 in. to 18-1/2 in. hanger bar. It is made with thermoplastic PVC for durability. Its hard-shell resists flexing and holds its shape in bad conditions and the box is fire rated and UL listed to help ensure safety.