We only have the "kid" k'nex which are the larger ones, and my dd 4.5 loves them. I bought them for her older brothers a few years back and they have gotten quite a bit of play over the years. My dd tends to make belts, hats, and other wearables with them and there is a set that makes a bird type of thing that they love the noise making part of (gets used in many of her "fashions").