Shrinking Disc

Hi, Guys and Gals:

Does anyone have any experience with the use of a shrinking disc in relation to bodywork?

Recently went to a Good Guy's show (Pleasanton, Ca.) and came across a booth (Sunchaser) where a guy took a banged up fender, roughed it out with a dolly and hammer, then too a ribbed shrinking disc to it - to the point the fender was back to it's original shape. Needless to say would require no BONDO, FILLER, etc.....

Though I saw it with my own eyes....am I missing something here??? I mean, if this is all possible why do I here more about fillers than shrinking discs???

Anyhow, would love to hear your experienced thoughts on this subject.

Thank you for your time.

Shrinking discs have been around for years, it takes a little practice and skill to use one and most guys are afraid of them, with practice and careful use they are GREAT, I learned on my 36 Hudson front fenders, they were a complete disaster and I figured I couldn't hurt them, they came out beautiful.