Check out this thread on the "Hotrodder's Bulletin board." It's about a MIG welding wire called "Twenty Gauge":

http://www.hotrodders.com/showthread...t=twenty+gauge

The thread is quite long, and the are various people who get the info wrong at times. To summarize:

1 - The name has nothing to do with the size of the MIG wire. It's just the name the manufacturer came up with.

2 - It is NOT flux cored. You MUST use shielding gas with it.

3 - It is specifically designed for welding on thin sheet metal such as is used on car bodies.

In the thread, it's not entirely clear if it's softer than regular welding wire, but it apparently lays down a thinner bead, so less grinding is required.

I have not personally used it yet, but have been meaning to get some. As a result, I have no personal experience with it (yet).

Thanks,
PeterM