I also have some of the NeverFail masking drink. A buddy used it on parole and never failed, even after testing 24 hours after smoking. But I know some people say this is BS. Substitution is out. Dilution is a possiblity....but I am afraid of failing due to dilution.
Then you should be afraid of failing with the so-called NeverFail magic potion as well. Magic potions are nothing more than an overpriced Dilution recipe-in-a-bottle (when they do work). They "mask" by diluting your bladder so the urine sample registers below the screens cutoff thresholds. The same exact thing can be accomplished in N2's Dilution recipe (for many $$$ less).