Doctors, agree that Breastfeeding a Baby is one of the best decisions any new mom can make for their baby if they are able to. Not only does this have beneficial nutritional benefits, but it also promotes bonding and reduces the risk for postpartum depression. The pain and discomfort associated with breast feeding for some moms which makes this decision unbearable. We've been there and hence this nursing essentials gift set. Tested to ensure zero Chemical leaching, no BPA, leads, or Phthalates. Made up of : 2 inserts. This product has a variety of models, which can change the size of the "breast milk channel" on the cover of the breast pump, so as to be suitable for mothers with different nipple sizes, help to improve the breast feeding efficiency and increase the pumping capacity, and make mothers more comfortable in the process of breast feeding.EASY TO CLEAN: Boiling water safe, Steam safe, Dishwasher toprack safe. Food-safe, seamless design. Design for milk flow without blocking, do not reduce the suction of the original pump. BPA and DEHP Free. SAME SUCTION AS ORIGINAL PUMP PARTS. EASY TO INSTALL REMOVE. AVAILABLE IN 15, 17, 19, 21mm. MADE FROM SOFT SILICONE: Soft silicone makes pumping more comfortable, and suitable for moms with smaller nipples. Correct flange sizes make pumping more efficient. Seamless Compatibility For Optimal Milk Expression: Suitable for nipple diameter 16-18mm(BEFORE a pumping session), or measure the circumference of nipple base about 50.24-56.52mm(BEFORE a pumping session). COMPATIBLE PUMPS: Mompmuir 21mm Flange Inserts Compatible with S9 S12 Pro S10 Spectra S1 pump 24mm, Spectra S2 pump 24mm, Spectra Synergy Gold Dual Adjustable pump 24mm, Compatible with Medelaa Pump in Style with MaxFlow pump 24mm, Manual Harmony pump 24mm, Swing Maxi pump 24mm, Freestyle Flex pump 24mm, Symphony pump 24mm, Lactina pump 24mm, Sonata pump 24mm, PersonalFit Flex 24mm. Also fit Freemie pump 25mm. It will reduce the 24-25mm breast shields nipple tunnel down to 21mm. 2pcs each pack.