The female intimate organ, also known as the vagina, is an elastic muscular tube that extends from the vulva, which is the external Instruments, to the cervix of the uterus. The length of the vagina can vary depending on various factors such as age, sexual activity, and hormonal changes. On average, the vagina is about 3-6 inches long, but it can expand to accommodate different things, such as tampons, during menstruation, and during sexual intercourse to accommodate the penis.

https://medicalcaremedia.com/how-deep-is-the-female-intimate-organ/

When I was a little kid, I dey always hear 'inu obirin jin' in the context that you can't really trust them (women) completely. I never understood until I became sexually active, the context changed completely. Even till now, I'm amazed how the whole of my appendage dey enter woman fully.