If your child comes to you with this set, then you should change the mouthpiece at the latest, we had physician visits behind us because the abdominal pain never really went away, sometimes they were there then gone again, combined with diarrhea. No one could find anything! Now after the holidays when our son complained of abdominal pain, the whole week is not, we took his bottle for school before, we cut the mouthpiece with a knife and despite "clean as much as possible" a brown / black coating in the mouthpiece found. We now use water bottles with screw cap, which can also be thoroughly cleaned! The bottle are good in and of itself, but you should change weekly mouthpieces because it is almost impossible to get them clean! I hope with this resonance many children future complaints that may be related to this water bottle to take!
