Bought these to use with my Yellow Jacket gauge kit when working on a car air conditioner. The red adapter connects directly to the red hose (high side) and the blue adapter connects directly to the blue hose (low side). Now the yellow hose on your gauge is the one that connects to your vacuum pump or coolant canister/tank. The yellow hose does not normally require an adapter to connect to a vacuum pump, but an adapter will be required to connect to a faucet valve if you have a gauge kit such as the Yellow Jacket Series 42006. It is included with this conversion kit and is shown in the picture of the can tap shown. So with this kit you are quite safe from working with R134A. If you are a do-it-yourselfer and planning to get a full setup to work with your vehicle's air conditioning then this is my suggestion. This is the setup I bought and it works great for me. I didn't buy the most expensive gear, but I bought the good stuff. This is my list and should be bulletproof for you too. Yellow Jacket Manifold 42006 Series 41 with 3/8" Gauge, R-22/134A/404A2. Mastercool 85510 r134A can embed valve, screw model3. This conversion kit is here4. Robinair 15510 Vacumaster Single Stage Vacuum Pump 5cc ft/min It is recommended to a set of manifold pressure gauges to use with many different types of refrigerants, you can still use the above pressure gauges to work with R22 systems, and the vacuum pump can be used to evacuate all systems (just change the oil in the vacuum pump for each new task) Believe me, these are all solid products, good luck!
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