from memory (I might be wrong) - there are a couple of types. the 'standard' chu chu teat recommended for mixed feeding (like fattartsrock said) is a teat that functions more like a breast. I think there is another teat that is shaped differently again, and as you mentioned can be used for cleft palate etc. I bought mine from
here but i see too that breastmates sell them too.
i think the chu chu teat for palate issues actually has a flat side to it, so is slightly different from the one i have tried.
linky for that type of teat.