This 2pc base connector is wide neck and compatible with Spectra pumps S1, S2, M1, Spectra 9 and a range of other pumps and flanges. See product gallery for pumpin pal adapter set up. Compatible with wide mouth bottles like Avent, Spectra, etc. Easy to clean. Made of Bisphenol-A (BPA)/DEHP-free material and all components are steam safe for sterilization.