M.W.
Hi Nina, here is a web that will help you and sis pick the right one . I switched to BORN FREE and they are Great! they also grow with baby since they sell all compatible parts to turn them into training/sippy cups later on and they are kind of cute.they sell at babies r us, buy buy baby and Whole Foods. I'm glad you are making a difference in your child's life. look up healthychild.org for info. and thesoftlanding.com for shopping.
GOOD LUCK.