Shrinker/Stretcher

What type? Sheet metal, pipe swaging/expanding? Hammer types, clamp style?
I have a high dollar pair that I've had a long time and a cheap pair from HF. the only real difference is in the jaws. The high end pair have VERY hard reversible jaws. The ones from HF are softer and seem to lose bite faster. However I make my own replacements and now use good steel and harden them myself so the soft jaws are gone.
Get the heads and make your own stand and foot controls. Cheaper that way.

I don't do that kind of sheet metal work any more. But a good shrinker is invaluable. I can stretch with a hammer and torch.

I posted some information on a UK made set I bought some years ago in the drop box about 5 years ago
About 1991 I worked at a company that had a USA made set that looks like those sold by Frost in the UK and those mentioned in Ron Fournier's book, we compared the function and the ones I had were deemed vastly superior but also much more expensive, the difference was like night and day, the USA made set caused significant damage to the surface, compared to the ones I had. I presume this was due to the pre-loading mechanism on the ones I had requiring less bite into the metal compared to the USA made ones which seemed to require the jaws to bite into the metal rather than clamp it. I have not had the opportunity to try Eckold shrinker/ stretchers but they seem to be rated top notch AFAIK and priced accordingly.
The main thing seems to be the surface finish left after the shrinking process, spend more == less surface damage.

Yep sheet metal. Mostly aluminum.