This is the Estes Fin Alignment Guide, for ages 10 and up.
When building a model rocket one of the most difficult steps is attaching the balsa fins. Lining up the fins in the proper location takes a skilled eye and a steady hand. If the fins are slightly off it can change the trajectory of the model rocket. The fin alignment guide features easy to follow instructions which makes keeping your model rocket symmetrical much easier. The tool works on Estes rockets that are either four or three finned.