Product review (5 stars): Refrigerant tap saves vertical freezer.
Used this device to salvage an out-of-refrigerant, $800 vertical freezer, that was 9 years old.  Working good so far after a week. Hard part was only putting 5 oz of R134A in from a 12 oz can.  Over-charging has bad consequences.  Cost of the refrigerant was $5 at a sale last spring.  I recommend weighing the 12 oz can of R134A before and as charging, with the can valve on top to best monitor the refill process.  You leave this valve connected to the freezer, to seal it.