This pack of 2 BPA-free Spectra Small Cap Bottle Adapter is compatible with your Spectra Wide Neck Breast Shield to make them compatible with standard/narrow neck bottles such as Medela, Dr Brown, etc. Authentic replacement parts from the manufacturer. If you’re using narrow necked bottles with our wide neck shield, you can use these adapters so that you can pump directly into your bottles. Compatible with all Spectra breast pumps: Spectra S1, Spectra S2, Spectra 9 Plus, Spectra M1. If double pumping, order two for $12