Most women will find our medium size eggs (30x40mm) are the best size to start with.
The smaller the egg, the harder it is to feel it. If you gave vaginal birth recently or went through a menopause it might be easier for you to start with a larger egg. Though larger eggs are easier to feel they are also heavier, and harder to keep inside. You can still choose to start with a medium size egg, the choice is up to you.
Small eggs are not for petite women, but for advanced practitioners who have mastered control of their muscles and wish to advance their practice. You might also choose to start with a small egg if you are experiencing a lot of tightness at the entrance of your yoni.
If you are not sure which one to start with or desire to experiment with different sizes and crystals, opt for a set of yoni eggs of 3 different sizes. Read more about choosing a yoni egg.