Estes model rocket engine bulk packs are available in four total impulse ranges: 1/2A (mini engine), A, B or C (standard engines). These packs may be used for the rocket bulk packs or other Estes rockets. Whether you are launching rockets at school with students, at a youth group activity or rocket club monthly launch, Estes engine bulk packs are a must. Engine bulk packs come with all the rocket engine supplies you need to launch 12 rockets. Included are 12 rocket engines, 20 model rocket starters, 16 reusable starter plugs and 144 squares of recovery wadding. Use the C11-3 engine to launch these rockets: Green Eggs, Eggscaliber, Big Daddy and Odyssey.