We recently bought the transit set for a fourth birthday. The kids enjoy it, but there are not as many pieces as you might think from the package. The pieces maybe fill up one-third of the canister. The train and the car it pulls, shown on the front of the canister, use up all of the round connector pieces. I remember the canister of wooden Tinkertoys when I was growing up, and I'm pretty sure there were a lot more of the round connectors and rods in the basic set. The quality of the plastic pieces is a lot better than the old wooden ones, but don't expect to make anything big without buying multiple sets.