Actually women that are into fisting have to train their vagina's to take large objects like that. Most of us can barely take a cock on a good day!
I love fisting videos, never have been able to do it no matter how long we've tried. Some women are just naturally very loose, they didn't start out super tight in life and don't flinch at a womans fist or two or a regular man hand.
Women who are built like myself could never be trained to take more than 4 fingers. This guy yacking about someone taking double dildos, 12 inch long dildos, almost 11 lb babies.....they aren't women of my ilk, they would have set him straight a long as time ago about the average and smaller than average vagina.
Somehow this guy keeps equating length with girth abilities- if you can pass a large baby you must be long in the vagina, if you can be fisted you must be long in the vagina.
I've got a thousand clock hours of fisting vids behind me, when it comes to the Vag, i've never seen a woman take it more than wrist deep. It's not like insane ass fisting where you can throw your whole arm up into the armpit up there with a shoulder glove.
The vagina has limits, especially in length. The cellular structure of a vagina is built to stretch widthwise much more than length wise.