All buttercream Optimus Prime semi, for cousins birthday. Stacks are pretzel rods covered in butter cream. I used a 1/2 sheet cake and then divided it in 3rds, used two of the thirds stacked and other two I cut in 1/2 again and made two small square cakes with transformers logos... Kids loved it all. Biggest mistake was trying to fill the cake and then carve it.. I had minor leakage but used stiff frosting as a morter!!!