What do the letters and numbers on an engine mean?

The letter shows the total impulse class, the first number is average thrust, and the last number is the delay before the recovery charge fires.

How do I know which engines fit a rocket?

Most kits list recommended engines in the instructions or on the packaging. Match both the size and the class listed there.

This idea is part of our model rockets guide, where you can compare every kind side by side.

Gift idea

Model rocket engine variety pack

Provides a range of thrust options for different rocket sizes and desired flight characteristics, perfect for repeat launches.

A model rocket engine variety pack gives a hobbyist several thrust options to try across different rockets and flying days. It suits anyone who already owns a rocket or launch set and wants to keep flying without a trip back to the hobby shop.

Good for

Usually $15–$25Model rockets

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Why model rocket engine variety pack make a good gift

Engines are used up with every flight, so a fresh supply is always useful.
Different power classes let the recipient compare altitudes and flight behaviour with the same rocket.
Makes a practical companion gift to a rocket kit received the same Christmas.

What to look for

Match the engine diameter and length to the motor mount in the recipient's rockets.
Check the letter code and delay number against each rocket's recommended engine list.
See whether igniters and recovery wadding are included, or add them to the gift.

Kinds worth searching

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Low-power starter engines
C class engines
Engines with igniters

Questions people ask

What do the letters and numbers on an engine mean?: The letter shows the total impulse class, the first number is average thrust, and the last number is the delay before the recovery charge fires.
How do I know which engines fit a rocket?: Most kits list recommended engines in the instructions or on the packaging. Match both the size and the class listed there.

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Representative photo-style image of beginner model rocket kit — generated, not a specific product

Gift ideaUsually $25–$50

Model rocket engine variety pack

Why model rocket engine variety pack make a good gift

What to look for

Kinds worth searching

Questions people ask

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