Since your breast shield size is also dependent on breast tissue and skin elasticity, it is important to confirm you’ve chosen the correct size. Here is how to check:

Using the breast shield size you have chosen, center your nipple and gently hold the breast shield against your breast. 

Note: Please keep in mind that no two breasts are identical. Many pumpers use a different size breast shield on each side. Your size may also change throughout the course of your breastfeeding journey.