Women do not so much care about the length of what goes into the vagina (penis, dilator, sexual toys) because it will only fit as deep as her vagina allows.
However, the physical feeling that does matter to a woman is that of girth (width) expansion. A better yet definition of that sensation is ‘fullness’ – a gradual process of stretching with neurological learning.
Confused? Liken it to drinking from a straw, then taking a small bite, then eating a big sandwich that requires a full jaw opening.
The vagina is built to acomodate a full size penis and the sensation of fullness is a natural component of vaginal use. Women with vaginismus or women who lost vaginal elasticity (menopause, after cancer treatment) may need professional intervention to accept ‘fullness’ and use their vagina freely.