If I tell you, I have to kill you then.:nono::thumbup: All kidding aside, it is called 3X Rust Dissolver and, I did make a mistake, it is $13.99 per quart. I bought it from Speedway, part number 307-99024, and I can't say enough good about it. The stuff really works. I have a whole lot of surface rust on my whole project just from sitting. Has never been outdoors, but sitting unprimed and unpainted. I didn't even have to wire brush or anything. I bought a whole pack, 20, of cheap 2" foam brushes from Wally World (Wal-Mart) for $3.97 Bruch this stuff on and you can immediately see it dissolving the rust. I let it sit about 1/2 hour, keeping it wet as directed on the bottle. When all is dissolved, I use paper towels to wipe off. Then wipe off again with mineral spirits. Walla. ready to prime. By the way, I did my whole rear axle housing, 4 bars, 2 brake drums and 2 front control arms on just a little less than a quart. That also included practicing first on some old scrap pieces of metal.