Materials

This is a string of two vaginal balls with internal free-moving balls all completely covered in body-safe, nonporous silicone. The product page gives these vaginal balls a safety rating of 8 because the balls are made of plastic, but this rating is incorrect. The Lia Love Balls are completely covered in 100% silicone, and no plastic would touch the body unless they were to tear. Other products that are merely coated in silicone (like vibrators with internal batteries and motors not made of silicone) are given safety ratings of 10. So unless this is some lower grade of silicone, these are a 10 on the safety scale! This is an advantage over pricier brands (such as the Lelo Luna system) that use a non-sterilizable nylon retrieval cord.
The great thing about silicone is how easy it is to sterilize; just soak it in a 10% bleach solution. For day-to-day cleaning, just wash with soap and water or your favorite toy cleaner. Remember to use only water-based lubes so as not to dissolve the silicone!

Use
The Lia Love Balls are meant to be worn vaginally, to remind you to do your Kegel exercises, or even to subconsciously cause you to work your pelvic floor muscles simply due to their presence and weight. Kegel exercises (after Dr. Kegel who introduced them into the medical literature in the 50s) are the squeezing, holding briefly, and releasing of pelvic floor muscles. If you aren't already familiar with Kegels and cannot find the correct muscle, simply stop the flow while peeing. That's the muscle you want! (However, once you've found the muscle, don't make a habit of starting and stopping urine flow. It's bad for you to exercise your Kegels while peeing, and good for you while not!) Kegel exercises are done for medical reasons: improving bladder control, preventing various organ prolapse, restrengthening after childbirth, or sexual reasons: the ability to squeeze on your partner during intercourse, increased orgasm intensity.
To use the Lia Love Balls, apply a bit of lube (water-based only), insert them, and go about your normal activities, sexual or otherwise. Try walking, jumping, or even riding in a car, and you might feel some jiggling from the internal balls' movements. I didn't. If you don't like large toys for insertion, you will probably, like me, find these a bit difficult and uncomfortable to insert. Try your favorite tampon-insertion position, such as standing with one leg up at chair-height.
When its time to remove them, if you simply tug on the string, it stretches enough that I fear it might break! It's better to bear down on them and push them out with your vaginal muscles, using the retrieval string more as a guide. The stronger the Kegel muscles you are trying to strengthen become, the harder it's going to be to pull something from their grip! So, at the very least, you relax your pelvic floor muscles as you remove the balls. I found actively pushing them out to be intuitive, but some people might not.

Performance
Vaginal balls generally work in one of two ways:
-The traditional Ben-Wa balls are small and heavy, requiring you to squeeze your muscles just to hold them in.
-The currently trendy exercise balls are large and have an internal ball that moves freely, providing a rumbly sensation when you move.
For the average user, Lia Love Balls are too large to be a challenge to hold in.
And they don't rumble! I found the internal balls in the Lia Love Balls almost imperceptible. When holding them in my hand, if I hadn't known they had internal free-moving balls, I might not have noticed it. It required a fast sharp movement such as jumping to notice the internal balls, and then I was hearing them, not feeling them. I was able to feel the rhythmic movement of the balls while holding them in my hand walking up the stairs, but nothing strong enough to feel vaginally. I think there are two problems contributing to the lack of rumble in the Lia Love Balls. One, the internal ball is too large relative to its casing. Since all parts of the internal ball are always close to the wall of the hollow ball, it rolls smoothly, rather than knocking around. There's just no room for it to knock around! Two, the silicone coating absorbs some of the force of the impact of the internal ball, making it weaker, so you are less likely to feel it.
With no squeeze required and no rumble, the Lia Love Balls don't actually do anything! If wearing them makes you feel sexy, or reminds you do your Kegels, these have some function for you, but for me, they seemed to have none!

As my first sex toy purchased, I was disappointed. They were uncomfortable to put in and then did nothing. I'm still intrigued both by the idea of strengthening my sexual muscles and by the idea of purely mechanical vibration without batteries or motors! Thus I will continue on in my quests for a great Kegel exerciser (from what I've read, a heavy wand) and for vaginal balls with a rumbly sensation. Based on my research so far, I want something plastic (as the silicone partially absorbs and thereby dulls the impact of the internal balls) with a small internal ball, and I may have to try a few sizes: small enough to be comfortable, but large enough to feel!