I used Freeze-12 in a Cavalier c7-483 machine and was pleased with the results.  I could hang meat in it if I wanted to.  I had it cycling at 35 degrees and then turned the Tstat down just to see how cold it would get in the box and after about 4 hours it hit 16 degrees.  Best thing about freeze-12 is I did not need a certificate to buy it and it is a cheap r-12 replacement. Paid 29 bucks for 3 cans and that included shipping.  I had actually over charged the box, it only requires 90% of the normal charge of R-12. So be aware of that if you use it.