Sizing Inserts make pumping more comfortable for mothers with smaller flange sizes Improves fit and comfort for moms who need a flange size smaller than 21mm Flexible silicone material for a snug, secure fit Fits into Willow 3.0 and Willow Go 24mm Flanges and Containers only (sold separately) Nipple Measurements: 11-13mm nipple use Insert Size 15mm; 13-15mm nipple use Insert Size 17mm; 15-17mm nipple use Insert Size 19mm Easy to assemble and clean 2 pack Dishwasher safe Not made with BPA
