Great way to have adjustable and even voltage in demanding situations. 0-140v well built, time tested, american made.
Negative Product Points
As with any 20+ amp variac it's big and heavy
I use my variac for roasting and on my espresso machine. Can't say enough about how this helps in roasting. I have an isolated heating element line in my hybrid homebuilt. I can boost or cut down the voltage to vary my temp. output.Don't worry about getting one with a needle meter, I added a digital "Kill-A-Watt' meter for accurate readings(highly recommend). The quality of the Staco variac is truly classic american engineering and manufacturing. All parts are industrial quality. Great quality cord. The adjustment dial runs smooth and accurate. I heard of too many failures with variacs now produced in China to take a chance on them. I use it with my espresso machine to keep my voltage stable. Variacs should not be used outside of any electronics suggested range. Avoid keeping your variac in a humid environment for extended periods of time to avoid internal corrosion.
ebay buyer beware, there are some great used variacs and some junk too, be patient. with some time I got a good one.