This is a small model rocket intended to use estes "tiny" (1/2 A, 1/4 A) engines. One set of fins is different than the other set of fins, in shape and size. I have tested this rocket, and it should fly, but the nosecones requires a bit of sanding to fit. There are three types of nosecones: classic, rounded, and nearly flat. Choose whichever one best suits your taste, or experiment to see which one makes for the highest rocket launch.Nosecone: Infill: 100 percent Body: infill: below 25 percent Fins: infill: below 25 percentMake sure you use lots of recovery wadding, and connect a rubber band to the nosecone and the body via plastic glue. Sand the lower 1/2 in of the body, then slip the fins over the body, and plastic glue them too. Preferably, tie a small streamer to the middle of the rubber band to slow the rockets descent. The rocket should be so light that it will not break upon impact with the ground. Most of all, use common sense when launching this rocket. Do not launch the rocket at someone, do not launch the rocket during an electrical storm, and launch the rocket in a field that is at least 500 feet wide. Have Fun!Decross