Primal Grow Pro Will it be like being a teenager all over again? In many ways, yes it will. The main difference with the growth this time around is that it is localised (just on your manhood) and also, you are in control. If you just want to add an inch or two then all you have to do is use a natural enhancement plan for a maximum of two weeks, whereas if you are looking to gain a good 3 or 4 inches then you will probably want to continue for up to 4 weeks. Most men report 2 to 4 inch gains after 1 month so this is a good time frame to consider.