Knowing what is available for which you can add extra inches and coming to grips with which option you should consider!
Most are and all tend to be sold by manufacturers which should be checked to see if the idea behind it being safe.
Finally speaking to the side effects, then you will need to be aware of the side effects associated with more common products which are easily available over the net.
This is where you need to look and the extent your knowledge will aid you in this area and any information which is available will help.
Herbalists have found them useful in some cases and have relied on them over the internet for a number of years for achieving that degree of effectiveness.