This was a very enjoyable ride to build. However, like all K'nex products I have built, it suffers from a multitude of small parts which are difficult to hold, compounded by being made of a slippery plastic that compounds the problem. Another defect is in the illustrations, I often found then almost indecipherable but I plugged away and got through. Part of it is my fault, I am too old to retain full use of all my joints, I am partly color blind and have trouble discerning what part is called for but I still enjoyed building the models. And when I am done and turn them on, to see them work, then all my effort becomes worthwhile.