3MFire Barrier Moldable Putty Stix MP, 1.45 in x 6 in

I use this for blocking holes in engine firewalls. It molds easily around cables and wires and sticks well to block the holes. I have not checked its fire resistance. After a year it is still flexible and stuck in place. Does the job of blocking fumes from making their way out of the engine compartment.

I needed something to block openings around the electrical boxes for lights and smoke detectors in my ceiling, and this is a much better option than only using caulk (at least in areas where the red color doesn't show). I'm impressed with how easy it is to mold into the right shape with its putty consistency - as well as its ability to be stuffed into odd shaped openings. The fire retardant capability is a great plus

Very workable and hopefully flame proof putty. Easy to work with and good to put a temporary seal around air drafts.

I bought this to fireblock a short 2-foot conduit I ran from the electrical panels in my garage through the rim joist into the basement to carry a bunch of yellow 12 gauge Romex wire. The inspector didn't care if I fireblocked it or not but I did, as I also want to keep bugs from using the conduit as a superhighway and I try to keep my house as tightly air-sealed as possible.This stuff was easily moldable and mashable and did the job with no problem. I sealed the conduit from both ends for good measure. I have a bit leftover from the job that should keep for a long time in the original tube.

Just needed a little bit, now I have 90 percent of it left