Small is recommended for users under 30 and who have never given birth vaginally. Large is recommended for users over 30 or who have given birth vaginally at any age.
However, it is important to consider other factors such as cervix height, bladder sensitivity, and the heaviness of your flow in addition to your age and the strength of your pelvic floor muscles
Please visit theSize Guidesection to determine which size to purchase if you are unsure.