A breast pump flange is the funnel-shaped piece that fits over the nipple and areola during pumping. It creates a seal around the breast, allowing the pump to extract milk effectively. Choosing the correct flange size is essential to ensure proper milk flow and prevent discomfort or nipple damage. The 24mm flange size/shield comes with each breast pump. Additional flanges, compatible with the 24mm breast shield are available separately, either as a kit or in pairs - Universal Silicone Flange Kit (13-21mm) Takes the guesswork out choosing what size you may need. It is also common for nipples to gradually change size during your breastfeeding journey Includes a Bubka Flange Ruler to ensure you are using the correct flange size The Kit includes 10 pieces - 2 x 13mm, 2 x 15mm, 2x 17mm, 2 x 19mm, 2 x 21mm flanges Bubka Breast Pump Flanges As per your specified size Choose a pair of flanges in sizes 2 x 15mm, 2 x 17mm, 2 x 19mm, 2 x 21mm, 2 x 27mm Pro/OG or 27mm Move To help you determine the correct flange size: Measure your nipple diameterUsing a ruler, measure the diameter of your nipple at its base (see image) Add 2mm to your nipple diameter measurementTo allow for comfortable movement and prevent nipple rubbing Choose the closest flange sizeCompare your adjusted measurement to the available flange sizes and select the one that is closest in size. Universal Compatibility: Flange inserts are compatible with most major breast pump brands 24mm Breast Shield (Bubka, Spectra, Medela, Philips Avent, Momcozy).