17/19/21mm inserts are compatible with Medela, Spectra, Elvie, Willow, TSRETE, Bellababy, Momcozy, and NCVI 24mm breast shields. These inserts reduce the 24mm shield nipple tunnel size to 17/19/21mm and are also compatible with most other brands featuring 24-25mm connectors, including Freemie. Made from BPA-free materials, they ensure a high level of safety for infants. Designed to improve milk expression efficiency, these inserts help maximize milk output while reducing the risk of nipple discomfort or irritation. They are ideal for mothers with smaller nipples who use larger breast shields, providing a proper fit for more comfortable and effective pumping. The inserts are easy to clean and can be washed with warm water or placed on the top rack of a dishwasher. Package includes 3 breast shield inserts.