So from everything I have known about the "synthetic" urine is that it is actually just dehydrated urine, that has been a while ago though so it may have changed. But I am assuming that you are asking because you need to pee in a cup for something or other. If that is the case then I would go with the dehydrated urine stuff because it is real pee, real clean pee hahaha. They even have male and female pee pee I think. If you are asking something specific about synthetic urine my apologies. Also if you are peeing in a cup is it going to a lab or is it the old skool strip test?