I bought new duckbills for my spectra s2 and it's perfect. No concerns . So much better than the ones that came with the actual pump .
Includes 4 duckbill valves for the Spectra S1, S2 or 9. This is a Maymom product.
It's important to regularly change out these valves for optimum pumping output.
Can also be used with Medela pumps if you prefer them to the valves and membranes.