Adapter fittings designed to work with 1/2″ ACME left hand threads. R-1234yf has gained acceptance in the automotive market but is just being experimented with in the HVAC market, mainly by customers who are working on freezers and small charge refrigeration systems. There are some mild flammability issues with this refrigerant, so until they are worked out we are not openly pushing this product, however, we want you to know that it is available.