Estes 3 Packs of A8-3 Model Rocket Engines - Total of 9 Engines with Starters & Plugs (1598PK3)PLEASE NOTE: These are 18mm diameter engines. Please refer to the instructions that came with your rocket (or the rocket's product description) to determine engine compatibility. 3 Packs of Estes A8 3 engines total of 9 engines (each pack includes 3 engines, 4 starters, and 4 starter plugs) The A8 3 is a single stage engine designed for model rocket flights weighing less than 3 ounces, including the engine. This engine is ideal for smaller fields, or