a very important spare part for breast pump, anti backflow to avoid your breastmilk back flow into the tubing.
It is very hard to cleaning the tubing, so we need this part to prevent it happen.
I use this in my spectra pump and freemie too!
Very useful item!

These are really great and work perfectly with my wife's Medela's electrical pump personal fit parts!

My Wife would prefer using these over the original backflow protectors with the adapters, mostly because it's a simpler set up and easier to clean. Highly recommend these!