The Wide Neck Breastmilk Collection n Storage Bottles allow you to pump, collect and store all in one bottle. Compatible with Spectra S2/S1/9 Plus widemouth flanges and bottle holder on the pump for pumping convenience. It's designed with SureSeal Sealing Disk for leak-free pumping and storing, and embossed graduation marks for easy tracking of bub's intake. BFA-free. Note: the bottle is semi-transparent due to it's thick wall.