This is version 3 of my Micro Model Rocket. It fits 13mm style Estes model rocket engines, A3-4T and A10-3T. Some extra parts are required to fly this model safely. You will need to add 9-10 grams of weight to the nose cavity, I used lead, and a launch lug glued to the body of the rocket, I used a cut off portion of a Bic pen. If set up correctly, this rocket should achieve heights of at least 300ft. THIS ROCKET DOES NOT HAVE A PARACHUTE OR RECOVERY SYSTEM. The rocket will eject the motor at the end of its burn and it will fall within a 100ft of the launch site (weather dependent) Make sure all people and animals are a safe distance away from the launch site and landing zone of the rocket. All of the rockets I have launched have been recoverable and able to launch again. Feel free to adjust the print settings to best suit your needs. Enjoy :)