I bought Thomas, James, Annie, Clarabel and a Troublesome Truck for my 3 year old Nephew. He is having great fun with them even though they are not compatible with his Brio track. The Amazon website does not explain this. Only one side runs in the track, the other side runs over the 'sleepers' if there were any. He still finds it great fun but I wonder what will happen when he is older and realises the problem. We will probably buy some Learning Curve track for Christmas so that he can run Thomas and friends on their own track, going under bridges on the Brio. He can pretend its the island of Sodor.