The FRANZIS engine kits are wonderful to look at, and are designed for anyone who wants to understand and explain the technology of reciprocating internal combustion engines. The detailed replicas of classic engine concepts offer full visibility thanks to the transparent plastic housing. The crankshaft and camshaft, pistons and connecting rods as well as the entire valve train of the functional models are movable just like the original. Even the ignition sparks are simulated with LEDs. As with the models used as an example, the individual parts of the FRANZIS model engines are screwed or plugged together. The accompanying book with detailed building instructions helps and provides a lot of interesting background information.