17/19/21mm inserts are compatible with Medela, Spectra, Elvie, Willow, TSRETE, Bellababy, Momcozy, and NCVI 24mm breast shields. They reduce the 24mm shielded nipple tunnel to 17/19/21mm. Also compatible with most other brands with 24-25mm models, including Freemie. Made from BPA-free materials to ensure safety for your baby. This accessory helps improve breast shield efficiency and maximize milk expression while helping to prevent nipple discomfort or irritation. Ideal for mothers with smaller nipples using larger breast shields, where proper nipple tunnel fit is important for comfortable and effective milk expression. Easy to clean—wash with warm water or place on the top rack of the dishwasher. Package includes 3 breast shield inserts. If you have any questions or need assistance, please . Our team is here to support you. Your satisfaction is our priority. Thank you for choosing our product.