3M™ 7100265894 Fire Barrier Electrical Box Inserts EBI-4, 3.25 in x 3.25 in x 3/16 in, 40 Each/Case

3M™ Fire Barrier Electrical Box Inserts are a flexible, one-piece fire-rated intumescent insert used to protect electrical boxes by adhering to the inside the box. When exposed to fire, the insert expands to fill up the box preventing the spread of fire and limiting temperature rise.