Alex17inch: The servix is very small, but it is very strongly flexible that a baby can arrive with the birth through it. So it is also possible to push your penis through it.
But it was for all woman, who tried it, very painfully the first time, therefore I have large respect for each woman, who was ready to take in my full size.
In addition the sex is many more beautiful and more intensive, if I can fuck her with my full length. And nearly all women, who tried it, love now the feeling to feel it deeply in her uterus and enjoy it.
A average vagina is six inches in depth. So the problem is the servix. If you with each impact pushes against it or penetrates through, it is very painfull for a woman. But a cock over 11 inch can stay with the penis head inside of the uterus and can fuck hard without problems.