DESCRIPTION: Please check the Size Chart [https://cdn.shopify.com/s/files/1/0733/9615/8785/files/555813_325576_480x480.webp?v=1681948832] before ordering as our flanges have a different design than traditional plastic flanges and sizes from different brands are not directly comparable. BabyMotion Flange transforms pumping into nursing by mimicking a baby's suckling motions. It stimulates nipple and areola, increases pumping efficiency, is soft and comfortable. Directly compatible with all Medela, Lansinoh, and Hygia pumps. Please check the FAQs section for how to use with other pumps. The 3rd Gen has clear tunnels for better centering but the material is slightly stiffer than the 4th Gen so it might not be as comfortable. BPA free. Food Grade. Includes a pair for double pumping.