Inserting ground up bits of oak gall will, at best, do nothing. At worst, it will give you a raging infection. The galls contain intense astringents, which dry out and irritate your vagina. Disturbingly, some of the oak gall sellers advocate for drying out your vagina, as it will increase friction between you and a male partner's penis. Technically that's true—it would increase friction. It would increase friction to the point that you could get abrasions inside of your vagina. Is that what you want? Think about how painful rug burn is. Now picture that inside of you. Even if it did help your vaginal muscle tone, internal rug burn doesn't seem worth it.