Made out of 100% premium silicone. The circle-cut lid is for the straw insert. The star-cut lid (snack attachment) converts the Mini Cup into a snack container. The opening helps to hold the snacks from falling out of the container if flipped over. This attachment also gives access for little hands to reach into the bites. It is easy to store and carry along the snacks while on the run. The snack attachment encourages BLW, supports independence and helps with the development of fine motor skills. Easily cleaned, does not stain. Healthy alternative to plastic. Hand wash and sterilizer safe.