I don't understand when I bought it but that is for the new R-1234yf refrigerant which uses reverse thread cans to mix with R Avoid -134a. This will not work with R-134a cartridges as they are left-hand threads. For R-134a, search "Self-Sealing Tap R134A Right Hand Thread". However if you need a new R-1234yf this is a very well built valve and I recommend it.
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VIVOHOME 220LB HVAC Electronic Digital Refrigerant Charging Weight Scale β High Precision with Protective Case
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