As far as I know, there are products that work, and those that are total scams. Now, for the ones that actually do work, they tend to be hyped up. For example, there are pills that will give you a bigger load, only the increase is so minute that it's almost pointless. So in other words, whether the pill works or not, it's still not worth it.
But if you are still interested in trying something anyway, go with maca root. It's 100% pure dried root extract, and it works. It's been proven to increase sex drive and semen volume. There are no side-effects except for tasting like crap.
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ukey: If you get it, make sure you get the pills, not the powder.