The Maymom Breastmilk Storage Bag Adapters are designed for use with Spectra S1 and S2 pumps, as well as Avent Comfort wide mouth flange pumps. This set includes two adapters made from clear, BPA-free polypropylene material, ensuring safety and durability. The patented design allows you to pump directly into popular breastmilk storage bags like Lansinoh and Nuk, eliminating the risk of milk loss during transfer. The adapters fit most wide neck breastshields, making them versatile for various pumping needs. They are safe for boiling water sterilization but should not be placed in a microwave or steamer. The clear material allows you to see the milk flow during pumping, enhancing the experience for mothers.