I had purchased a few bottles of Prolong Power from their website several months ago, but ran out. I thought it was just a short-term use, but soon afterward I noticed that I was more tired than usual. The Prolong Power was the only factor that had changed, so I began shopping for more. It apparently comes in different formulas, and the ones I bought aren't quite the same as before, but they ARE working. My tiredness has gone away. Walmart had the best price and quantity that I could find on the Internet.
In advertising, these were originally promoted as increasing your sex drive, but more currently speak only of energy in general. They do seem to be working in both areas.