[dicklague]

most of these A/C products are propane based. Propane is a much more efficient refrigerant than 134 so you need less.

Licensed shops won't touch it because by state law they have to use and dispose 134 properly. Propane is a natural gas and can be vented to the atmosphere.

Use a vacuum pump and a set of gauges when you install this stuff. I did it on our Chevy trucks and it worked very well.

there were some posts here on this site about these gases so do a search and you will find lots of discussion.

They do work well in older 911 A/C installations. Do some Google searches and you will find lots of sources.