quote from their site.
"Autofrost
High Performance R-12 Replacement.

Autofrost is completely compatible with all existing system components. Simply pull out the existing refrigerant and charge in Autofrost. Autofrost is sold in 25 lb. cylinders and cases of 12, 9.6 oz. cans. By far the best replacement on the market today. "

BUT I've just dumped some into a system that had R12 in it and I haven't had any problems.