What ever you do, DONT put that stuff in there, it will fix the problem for a short time then it will screw up your system. We had to work on a car one day that had that stuff in it, and the bill was more than what the car was worth, just for a small hole in a line. i would find the leak and fix it right so you dont end up wasting your money.
Are you talking about the R134A? I've used the stop leak, leak detector, oil charge and the freon with good results.
Back when I used to work for Wally-World they had a bunch of $30-$40 kits for $5 and under. I bought a bunch of all of it and have used it on several cars. My personal experience is it'll work but like said before for a permanent forever fix you need to replace the O-Rings, Gaskets or whatever is leaking it off.
The Stop-Leak sometimes works better than others, depending on the severity of the leak.
I will shamefully say i've used it :embarassed:. It must've been a pretty small leak in my system though, cause once we put some more R134 in, it cooled like a champ all summer. I know its not apermanent fix, but its what i could afford at the time. If it stops working, i'll just roll the windows down. I usually dont use the AC anyway, but when my wife's in my truck she wants in cool, and she's easier to get along with when she's cool.