Interesting ad for DuraCool on ebay. Check it out:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6765&item=2417723854
No slam against anyone trying to make a living selling this stuff for a living but in my opinion, this ad is kinda misleading because in there they state it is a "drop in" replacement refrigerent. This is scary because I can see someone adding it to a R12 system. The ad may have explained it in more detail but I did not have time to read all the way through it.