[Essential accessories for pumping - Some moms have the experience of nipple uncomfortable while milking these flange inserts helps. The silicone cups are 24mm so if your nipples need a different cup size do get inserts to use reduce 24mm flange down to other size. Our flange inserts comes with 5 different sizes 13mm 15mm 17mm 19mm 21mm 1pc for each size for you to choose the right size for your nipples make you more comfier when pumping Compatibility - The breast pump flange insert sets include 5pcs flange inserts 13/15/17/19/21mm 1pc for each size 1pcs silicone diaphragm 1pcs duckbill valve. Those flange inserts suitable for 24mm Shields/Flanges compatible with Momcozy wearable breast pump S12 Pro/S9 Pro/S12/S9/TSRETE/Spectra/Medela/any S9/S9Pro/S10/S10Pro/S12/S12Pro/S12A/S13/S15 wearable breast pump. Silicone diaphragm and duckbill valve only compatible with Momcozy "BPA free the silicone flanges are made of food grade silicone which is very safe soft and odorless so you can feel completely at ease with your babys milk." Wash pump parts after every use with warm soapy water and rinse well.]