This is the best cheapest option for Replacing R134A  or R12 Gas in  air conditioner system on Cars or Trucks . Note all Air conditioning repairs And servicing need  suitably qualified people to do  these job and wearing Safety glasses and gloves as the Gas does cause burns to human part . This gas does not mix with R134A so needs to be put in and empty system and really needs the oil changed as well . It is very easy to overcharge the system using this gas so dont put to much in a one time and thats why you need a tap that turns off