3 cans of Dye Charge for R1234yf systems and charging hose Enviro-Safe Dye Charge is fully compatible with mineral, ester and pag oils. For use in 1234YF automotive applications. Highly concentrated dye (fluorescent yellow) In some cases, you can see the dye with the naked eye. The dye works best with the use of a black light and UV glasses. #3565 UV Glasses #3525 Black light This is the same color dye that most auto makers inject into the vehicle when new. This has a piercing valve on the hose. You must back the pin out once screwed down to allow the product to flow out of the can.