Medela PersonalFit Breastshields are designed to accommodate different nipple sizes. They are available in five different sizes, allowing
mothers to choose exactly the right breastshield size for them to
ensure maximum comfort and output whilst expressing milk. Pumping
should be comfortable!
24mm shield is the medium size made by Medela. This is a size that is commonly chosen by moms,
size shield that Medela provides with new Medela breastpumps is the
medium (24 mm). Some pumps also come with the large (28mm) size. You
can verify size size by of a shield by looking at the outside of the
flange and searching for small, raised text that will read the size.
Based on that size, you can change the size you are using to meet your
Size up if you have large nipples and they rub against the inside of
the shield when you pump causing some discomfort (and maybe even
incomplete emptying of the breast) and/or if pumping is actually painful to the nipple.
Size Down if the nipple is not pulled down into the breastshield when pumping.