Levels four and five constructed. This is the level that you start tinkering together with engine and putting precisely the inside as fine. The higher the level you go, better work you may putting onto it. All of the levels have another age limitations. Yet, this is just what you think is suitable to begin to use the gear. It takes into account the fumes from the glue, paint etc., the skill for each level, and so on. What it all comes from though is how comfortable you feel with what you're doing. Some people get it does not easily, in order that they fly by skill levels one and two