Ⅰ. Package Content: You will receive 10 pieces of flange inserts (13/15/17/19/21mm), 2 pieces of each size. The quantity can meet your daily use and replacement needs. Ⅱ. Compatible with: Our flange inserts can be used with most 24mm shields/flanges and are compatible with any S9 Pro/S12 Pro/S9/S12 wearable breast pump, such as with Momcozy S12 Pro/S9Pro/S12/S9 hands-free breast pump. Please note that our product is not sponsored or endorsed by, or affiliated with the brands it fits, including Momcozy, Medela, Spectra. Ⅲ. Comfortable to Use: The correct size of the flange insert is important for comfortable and efficient pumping. Chose the flange insert with a suitable size so that your nipple won't rub or be squished in the flange tunnel. It's recommended that you replace the flange insert every 1 to 2 months. Ⅳ. Premium Material: Our breast pump accessories are made of silicone. BPA-free. You can use them with confidence. Ⅴ. Easy to Clean: Rinse the pump parts with warm soap water and rinse well after each use.