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 to 17/19/21mm and are also compatible with most other brands that have 24-25mm connectors, including Freemie. Made from BPA-free materials, they ensure a high level of safety for your baby. This accessory helps improve breast shield efficiency, supports maximum milk expression, and helps prevent nipple discomfort or irritation. It is an ideal solution for mothers with smaller nipples who are using larger breast shields, where proper fit is essential for comfortable and effective pumping. The inserts are easy to cleanwash with warm soapy water or place on the top rack of the dishwasher. Package includes 3 inserts. If you have any questions or need assistance, please . Our team is committed to providing support and ensuring your satisfaction. Thank you for choosing our product.