Product review (5 stars): Really works
Sealed my 19-year old system right away. After AC guy topped off the R22, temperature at vents dropped from 74 to 66! Just buy this stuff, it really works.
BTW, in case you think I just needed to top off the system, not really. I had it topped off three times since spring and it never dropped the temperature that much. It's all about pressure. If you have leaks, there is no pressure to keep it cool enough.
I used one can for a 4-ton system.