This is a model rocket I designed for school. It uses engines you can find at a hobby store. The inner diameter of the rocket body is 19 mm, but is designed for engines that are 18mm with wadding sourounding it. Glue a straw onto the side so it can be put on a launch pad. The bottom part of the cone may need to be sanded down to fit in the upper body. I put screws in the in the cone for counterweight, and secured it with hot glue.