B4-4 Model Rocket Engines (3pk) – EST-1602

B4-4 Model Rocket Engines (3pk) – EST-1602 The Estes B4-4 is single stage engine designed for model rocket flight. This engine is a standard engine designed for flights in rockets weighing less than 3.5 ounces, including the engine. Each package includes 3 engines, 4 starters, and 4 plugs.