Spectra Baby wide-neck breast shield flange set includes: 1 Spectra Wide Neck Flange, 1 Spectra Backflow Protector, 1 Duckbill Valve and 1 Tube. If double pumping, please buy two sets. Parts are designed for use with the Spectra S2, S1, DEW 350, 9 Plus, and M1 breast pumps. This wide neck breast shield is also compatible with Spectra wide neck bottles. If double pumping, please buy two. 4 sizes available: 20mm, 24mm, 28mm, 32mm. Discounts for higher quantities.