Sippy Cup Which Sippy Cup Are Good For Start To Learn?

Which sippy cup are good for start to learn? - sippy cup

My son is not potty real, but Nuby Sippy cup with teat slow flow and smooth, she was with him fine, but when he tried to suck hard shell was not ready, everything we chew the nipple. How old were you go hard on the pot? because he is not willing to 15 months. Okay, he has a fresh cup in SIP?