I give it a 3 because its not quite as easy as they make it out to be, I used it on a aluminium AC condenser on a car that had rubbed thur against steel cleaned it well an it stuck well to one side tough to get it to stick to the other so it worked so far but not really sure ot the integrity of the braze. time will tell. I used propane and that is alittle under temp to make this work. MAPP or oxy acetlyene would probably be better and easier to get the base material hot enough to spread it and get a bond. Ill try again with either of those and report back.