ECOtanka's adaptor lid is designed to fit Avent teats and Avent easy sip spouts to tankas, to transform them into baby bottles, toddler bottles, or sip bottles that can be used by the disabled.  The adaptor lid is available as a separate item and fits all of the original tanka range except for the mega tanka.  Made from Polypropylene #5, it is 100% BPA free, safe and non-leaching.