straw has weighted ball so it will always moves to the liquid
SILIFLEX-straw technology, Valve-free
BPA and Phthalate free
This sippy cup isn't your ordinary one. The BOT Sippy Cups features the original SILIFLEX-straw technology that is designed with a weighted ball so the straw always moves to the liquid regardless of the orientation of the cup. With its valve-free flexible straw, weighted ball and integrated handle, both babies and toddlers will find it easy to sip to the last drop.
ZoLi BOT XL Straw Sippy Cup - Green 9 oz - B008XKIEFC