If internal stimulation is what you seek - then Oriental Orgasm Balls will do the trick. Orgasm Balls are two hard plastic balls about 1.25" in diameter (with smaller solid balls inside) and tied together with a cord. The effect when placed inside the vagina is that the heavier balls rock around when you move, creating a natural vibration. 

Orgasm Balls are versatile because you can wear them anytime, anywhere.  There are several ways to use Orgasm Balls - one way is to insert one ball and allow the other to hang on the string on the outside thus creating both internal and external stimulation.  Orgasm Balls can also be used to strengthen the vaginal muscles and create a great sensation when used with a vibrator. Experiment with insertion and removal while contracting and relaxing the vaginal muscles. Make sure to clean your Orgasm Balls properly. 

While many novices express alarm at the thought of inserting and removing the balls, it's relatively simple: just pop them in and squeeze them out. You may want to experiment with location; some people enjoy holding them lower in the vagina, while others try to position them directly behind their G-Spots. Just don't aim for the cervix. While you're unlikely to have a problem with them slipping past your body's gateway to the uterus, you probably won't enjoy any kind of clanging sensation that close to your cervix, a region some women find particularly sensitive.

Purchase plastic balls if you are a first timer; the metal balls tend to fall out if your pelvic floor muscles are not strong. Empty your bladder first; it will make it easier to hold the balls in.

Insert one ball at a time; this is easier done if one leg is lifted up. Squeeze the pelvic floor muscles and hold the balls in. You will notice a feeling of fullness and notice the balls pushing down, but after a while you will be used to it. It is sort of like wearing a tampon. Wear them for a few hours every day.

To remove the balls, you can lift up one leg and cough, or jump up and down. There is no way that the balls will 'disappear' into your body.

Beginner Tips:
When you first wear Orgasm Balls, stay home and do not do any heavy physical activity, the balls will fall out. If they do, wash them off with soap and water and put it back in. Going out while you are getting used to the Orgasm Balls, could be embarrassing if you sneeze in the supermarket and have them fall out! It will take a few weeks of regular wearing before your muscles will be able to hold them in during physical activity. Be patient!

Once you have no problem holding in the Orgasm balls, you can upgrade to metal balls and enjoy the benefits of strong pelvic floor muscles. It will pay off, especially when you are older or if you have given birth!

You can wear Orgasm Balls during sexual intercourse. This will add more fullness to your vagina and stimulate the penis as well. Using them during sex is also a good way to create more natural vaginal lubrication.