Package Content: You will receive 10 pieces of flange inserts in sizes 13mm, 15mm, 17mm, 19mm, and 21mm, with 2 pieces of each size. This quantity meets daily use and replacement needs. Compatible with: These flange inserts are designed to be used with most 24mm shields or flanges and are compatible with S9 Pro, S12 Pro, S9, and S12 wearable breast pumps. Please note that this product is not sponsored, endorsed by, or affiliated with any brand, including Momcozy, Medela, or Spectra. Comfortable to Use: Selecting the correct flange insert size is important for comfortable and efficient pumping. A properly fitting insert helps prevent nipple friction or compression within the flange tunnel. It is recommended to replace flange inserts every 1 to 2 months for optimal performance. Premium Material: Made from BPA-free silicone, these breast pump accessories are safe and reliable for regular use. Easy to Clean: Rinse all parts with warm soapy water and rinse thoroughly after each use.