A male’s penis has reached maturity by the time he reaches his 17th birthday. The average size of the adult penis for men 17 and over is 6 1/4 inches.
Although a man can reach maturity at an earlier or later age, it is unlikely that it is still occurring at 21.
It varies for a lot of men, although there is some evidence of a few men getting it about 21 or so
A male’s penis has reached maturity by the time he reaches his 17th birthday. The average size of the adult penis for men 17 and over is 6 1/4 inches.
Although a man can reach maturity at an earlier or later age, it is unlikely that it is still occurring at 21.
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