Maymom Flange for Spectra/Medela (Wide-Neck) is a breastshield and connector in one that connects to Spectra and Medela Breastpumps for pumping into wide-neck milk bottles. This one-piece design makes for easier cleaning, less chance of losing suction, and less parts to bring when you are on the go.Compatible with all Spectra pumps (S1/S2/M/9+) and older Spectra breastpumps (Dew 350, 360)Compatible with all Medela pumps except Sonata, Swing Single, Swing Maxi, FreeStyle, Harmony and Pump in StyleConnects directly to Spectra backflow protector; no need for yellow flange adaptor!Pumps into wide-neck milk bottles ONLY (e.g. Spectra Bottles, Philip Avent, etc)Flange and connector in oneMade from BPA free PP material.Steam safe, autoclaveable.One piece for easy cleaning.US FDA complianceChoose between 1 or 2 sets of breast shieldsFeaturesOne-piece design; easy to clean, less piece to keep, and less chance for suction power loss.All components are safe for steam sterilization, microwave sterilized or sterilized in boiling water.Compatible with all Medela pumps except Sonata, FreeStyle, Swing Maxi and Harmony.US FDA registered medical device; Comply with US FDA standards for containers that contact food and class II medical device.Standard sized 25 mm inner diameter is most comfortable for the majority of breast feeding moms. However, other sizes are available too.Other sizes to choose from -15, 17, 19, 21, 24, 26, 27, 29, 30, 34, 36 mm one-piece flanges For compatible valves, refer to product images.How to choose the right size of breastshields for you?The inner diameter of the breastshield (B) should be 1-2 mm larger than the diameter of your nipple (N). AFTER a pumping session or 3-5 mm BEFORE a pumping session. You should be able to see free movement of your nipple during pumping and there should be little or no suction of the areola into the tunnel of the breastshield.