Estes C11-3 Model Rocket Engine Pack - Includes 2 Engines with Starters & Plugs (1522)PLEASE NOTE: These are large (24mm diameter) engines that will only fit certain model rockets. Please refer to the instructions that came with your rocket (or the rocket's product description) to determine engine compatibility. Estes C11 3 engine pack includes 2 engines, 2 starters and 4 starter plugs The C11 3 is a single stage engine designed for model rockets with a maximum lift weight of less than 6 ounces. Recommended for use with the Super Mars