Can a woman take 15'' hard rock full length?

Answer 1

Not many women... there is a reason the average penis length is 5 - 7 inches; that's how deep a vaginal canal is too.

This honestly should not be bragged about (or lied about) so often. If you have a large dick, do your lady a favor and don't put it in the whole way. That can quite easily lead to tearing and cramping which is very painful and not at all pleasant, and will result in you not having sex with her for several days.