These engines can be used interchangeably for smaller model rockets and all fit 18 mm engine mounts,

This bulk pack includes everything you need to launch 24 times! Use this bulk pack to experiment with different engine impulses for an exciting youth group activity or engaging classroom experiment.

Included in this bulk pack:

• 6 A8-3 Engines
• 6 B6-4 Engines
• 6 C6-3 Engines
• 6 C6-5 Engines
• 30 Estes Starters
• 24 Engine Plugs
• 75 sheets of Recovery Wadding