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The Garmin Astro's "dog collar" can be mounted in a 4" diameter or larger rocket.  You may need a right angle SMA connector to position the antenna vertically to fit in your rocket's electronics bay. The tracking distance for the Astro is relatively short if buildings, trees, or terrain blocks line of sight between the transmitter and the receiver.  Therefore, you will probably need to purchase or build a high-gain antenna for the receiver.