three medical-grade silicone, air tight, sealing disks; available in aqua, orange, and green! they allow the pura bottles to be repurposed for use by adolescents and even adults! the colorful sealing disks can be used in the most obvious manner for breast milk storage but also allow our pura bottles to be used a small water bottles or even snack cups for school age kids as they are the perfect size for lunch boxes.