"You're not putting those in my butt," Anastasia tells Christian in Fifty Shades Darker when he shows her a set of Ben Wa balls. He doesn't; Christian inserts them into her vagina. Anastasia wears them all night long at an upscale party as a secret accessory. Afterwards, the balls are removed, and the two proceed to have their infamously hot sex.
Ben Wa balls — also referred to as love balls, smart balls, or Kegel balls — are weighted balls meant to be worn inside the vagina. They're an ancient method used to train the pelvic muscles, says Jessica Shepherd, MD, an Ob/Gyn at the University of Illinois at Chicago, and using them feels similar to doing Kegel exercises. But you don't have to actively do Kegels while wearing them, since the balls are weighted, so your pelvic muscles naturally work to hold them in place, explains Madeleine Castellanos, MD, an NYC-based sex therapist, on her blog.
For many people (including Anastasia), Ben Wa balls increase sexual sensation, since they're typically worn for a while before penetrative sex, and then taken out just prior to penetration. In my experience, wearing a pair for a few hours prior to penetrative intercourse wasn't as automatically orgasmic as Fifty Shades Darker would make it seem. But when it comes to strengthening pelvic floor muscles, reaping the sexual benefits is a long game — it takes time to build those muscles.
"When the pelvic floor is 'alert,' it lifts our spines up out of our pelvis a bit. When that happens, the walls of the vagina cinch like one of those Chinese finger traps and [sex] is much more pleasurable for both people," Michelle Weber, a personal trainer who specializes in pelvic-floor health, told Refinery29 last year. So I'd recommend focusing on the long-term benefits, rather than searching for instant gratification. That's not to say that using Ben Wa balls isn't a fun way to get in your Kegels, though — sharing a sexy secret with your partner (or simply knowing you're holding something in your vagina) can be super hot.
As far as how Ben Wa balls work, it's a good thing Christian didn't place them in Anastasia's butt, as they lack a flared, sturdy base like the ones found in butt plugs, so they can get lost inside your anus if you mistake them for anal beads (it happened to me). To insert Ben Wa balls, use your fingers to gently push them into your vagina, like you would a tampon (adding lube helps). Removing the balls is fairly simple, too. If the set includes a string, gently pull them out (again, like a tampon); if there's no string, simply crouch and use your pelvic floor muscles to squeeze them out. And don't forget to wash them with soap and warm water every time you use them.