Most of the benefits sound like magic but holding something like ben wa balls inside as a way to strengthen the vagina muscles seems plausible, like a kegel exercise.
> Overenthusiastic Kegel exercises or incorrectly done Kegel exercises are a cause of pelvic pain and pain with sex in my practice. Imagine how your biceps muscle (and then your shoulders and then your back) might feel if you walked around all day flexed holding a barbell? Right, now imagine your pelvic floor muscles doing this.
[1] https://drjengunter.wordpress.com/2017/01/17/dear-gwyneth-pa...