Before a long cross country drive I noticed that both of my exhaust headers on my Chevy had cracked. I've been researching what I can do to fix this and found a YouTube video explaining this cement. Decided to give it a try for a few bucks. I cleaned the collector, smeared it with cement - let it dry the next day, bake idle for 2 hours. - let him sit, take a short trip. Traveled 3 more states and returned home. I changed my headers :P. When I took them off I saw that one of the cracks was still sealed and the other one was starting to come loose. Because that's not the intended purpose of the product and it still worked well. I give him good grades. The packaging says it's black, but in my case it turned light gray.