Willow Pump Spill-Proof Milk Bags pumping on-the-go hassle-free. Patented, no-spill technology lets you pump in any position directly into self-sealing storage bags. Attach the bag inside the flange and connect the Willow Pump - then toss in your fridge or freezer when you’re finished. BPA free & recyclable. Exclusively for use with the Willow Wearable Breast Pump. 90-day limited manufacturer’s warranty.