Metacaulk® Box Guard™ is a one component fire rated insert for use with electrical boxes. It is inserted on the inside back wall of an electrical box, and is a highly intumescent firestop material. When exposed to fire, Metacaulk® BOX GUARD™ will expand forming a char that will seal off the opening and prevent the spread of flames and limit the temperature rise on the un-exposed surfaces. Metacaulk® BOX GUARD™ is applied by hand, and must comply with NEC 314.16 (formerly 370.16) or other applicable cable codes.