The nipple serves its purpose. My 13 mon. old son uses it just fine. The only issue I have, and this very well may just be my punk kid and not an issue with the bottle or nipple, but the nipple can be pushed through the top of the bottle. He then says "agua" and spills his drink while innocently making eye contact like its nothing -_- I refuse to buy a whole bunch of new sippys while he is still transitioning between bottle/breast/sippy so we will make this work. We just watch him when he uses it and every now and again he pulls a sly one on us when we look away. Im okay with that.