The set is recommended for age 8 upwards, but Harry understood all the concepts fine and the model was actually quite sturdy once built so it was certainly suitable for him. He could not have built it without help as the propeller and cord tying was quite tricky but he put all the cogs in. He took it away for half an hour after we did the initial demonstration and experimented with different objects tied to the cord then dangled over the staircase to see if they were heavy enough! He is looking forward to building a water wheel model and bicycle next. Thames and Kosmos make lots of different science kits and I am sure we will be trying out more of them in the future, as science is always a topic that is enthusiastically received in our house.