Yeah, the synthetic is the best bet UNLESS you live in North Carolina, South Carolina, New Jersy or Illinois. My husband has used it before, worked like a champ, then I tried to order some for my recent test and as of 6 months ago, they do not sell it in NC, it is now illegal. So, if you are in the other states you have no worries. I was so pissed! Good luck to you, this would be the only sure way to pass in only 10 days. Definately get a home test or 12 and try some different things.