An undrilled yoni egg is a semi-precious gemstone in the shape of an egg, with no hole drilled into it. A drilled yoni egg is one in which a small hole is drilled into it, where you can attach a string (of unflavored floss, cotton, hemp, or fishing wire). Some women prefer to attach the string, so that they can gently pull the string to expel the egg, similar to how a tampon comes out. Although it is unnecessary, many time beginner users feel comfortable with the string as a form of psychological security. In addition to this reason, some women elect the drilled eggs because they can tie the string to a small weight, and practice vaginal weight-lifting.
The undrilled eggs can also be used to strengthen the yoni because they naturally have weight in the eggs, so even just maintaining them inside the yoni can lead to the yoni growing stronger. In addition, the egg just sitting inside the yoni can help stimulate enhanced nerve-ending growth, so that you can become more aware of your yoni and enhance control of your yoni muscles.