I use this stuff, it takes about 3 tubes to fill both sides of the crossover. Even though the package says it’s good to 500 degrees, I have a few friends with the putty in place after 15-20 years. Needless to say, lots of carbon buildup. I first tried this after spending several hours on the aluminum plugs, lovingly ring, filing, test fitting, more grinding, etc only to have them start rattling after a short time. The paint holds up much better also.